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GT40 engine loping

Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=24848
Printed Date: March-28-2024 at 9:03pm


Topic: GT40 engine loping
Posted By: slmskrs
Subject: GT40 engine loping
Date Posted: February-12-2012 at 5:10am
I have always had a bit of a problem with engine loping. It will do it when very cold (winter) when launching, and also do it when the engine is hot and it has sat for a while (30 minutes or so with the engine compartment closed). The warmer it is, the worse it is (really bad in the summer).

When it is cold, it can last for 30 seconds or so but then smoothes out without doing much of anything. When it is hot, it can last that long or up to a minute and be bad enough that it stalls. Giving it throttle helps and speeds up it getting back to normal. I have no idean on the problem when it is cold, but I would suspect vapor lock when it is hot. But with MPFI and high pressure pump, I don't know how that would happen.

I have not put a pressure gauge on it to see if the pressure is going up and down when it is loping (I am in the process of replacing my original GT40 heads with new ones, so it will be a week or two before I can put it back in the water and test). I did have my low pressure pump fail last year and I replaced it (made no difference for this problem), and have not seen any problem with the high pressure pump in the fuel canister.

But since it is a continual and ongoing problem, I'm hoping someone has a suggestion.

Thanks,


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Gordon '97 Ski Nautique, GT40



Replies:
Posted By: Luchog
Date Posted: February-12-2012 at 11:09am
it's normal on cold starts, have you cleaned the IAC valve?

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http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique

Commander 351W


Posted By: eric lavine
Date Posted: February-12-2012 at 11:24am
Idle air control, as Luch suggests

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"the things you own will start to own you"


Posted By: slmskrs
Date Posted: February-12-2012 at 6:42pm
Good idea. I did that recently on one of my cars. Since I already have the throttle body/plenum off and am ready to take the intake manifold off in preparation for replacing the original GT40 heads, it will be really easy (much easier than the car), I'll go ahead and do that now.

Thanks!

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: February-13-2012 at 2:19am
Okay, so I pulled the IAC (ISCV) and cleaned the orifices in the throttle body, including the screen. The ISCV I pulled out of my car actually seats in the throttle body, so it is easy to clean where it seats after you've pulled it out. However, since the valve seat is part of the IAC, I can't clean that part.

My question before I start spaying the inside of the IAC on either side of the closed valve seat, I wanted to make sure it is fine to spray throttle body cleaner in there. I don't want to short it out, so would appreciate advising the best way to clean the valve (and seat).

Thanks,

Gordon

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Gordon '97 Ski Nautique, GT40


Posted By: Luchog
Date Posted: February-13-2012 at 8:42am
You could use a Q-tip soaped in body cleaner.

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http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique

Commander 351W


Posted By: Bri892001
Date Posted: February-13-2012 at 1:50pm
It also comes up with these motors that the fuel control relays can be troublesome.

I've also read that there is some kind of a clear tube within the Fuel Control Cell (if your boat has one) that can develop a crack and cause fuel pressure problems.

Also, fuel pressure regulator has come up as something to check.

But, usually problems that are related to temperature are often electrical in nature.


Posted By: slmskrs
Date Posted: February-14-2012 at 1:26am
I've replaced the tube in the fuel control cell (it developed a pin hole and lost pressure at higher speeds--the engine needed more fuel and too much fuel was going out the pin hole to supply it). That is always something to look at if you loose at power on the MPFI engines with the fuel control cell. I'm going to put my fuel pressure gauge back on it once I have the engine back together and watch it when it is loping when hot. That should help determine whether it is the regulator or something electrical.

Thanks!

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: February-14-2012 at 1:27am
On the cleaning with a cotton swab, how can you clean around the valve seat since the valve is closed? Is it possible to carefully open it manually to clean the seat?

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: March-10-2012 at 7:49pm
So, I got my new heads back on and it is running great. However, I still havd the warm loping issue. I took the ISCV out of the throttle body and cleaned it. I also cleaned the orifaces and the screen, hoping that it would go away. No such luck. The conditions for this are:

* Engine warm (usully pulling at least one set first)
* Warmish air temps (used to need to be hot, but it is getting worse; today with air in the low 60s it was doing it)
* Sitting for at least 20 minutes (engine cover closed, warm day, no air flow around engine).

I have not yet put the fuel pressure gauge on it yet to see what if anything is going on with the pressure. I don't think it is the high pressure fuel pump since when cold and once it has run for a minute, it is fine If the pump had some sort of thermal issue, I guess it could happen--but if that was the case, I would expect it to not start at all until cooled.

I replaced the low pressure fuel pump last summer, so I doubt it is that. Someone mentioned about a fuel relay. Does someone know where that would be on a GT40 MPEFI?

Also, it was mentioned that the fuel pressure regulator could be another item to check (I believe it is on the starboard side fuel rail). How would that be checked? Would it be popping wide open to bleed down the fuel pressure, then close, and keep going open and closed?

Thanks,

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Gordon '97 Ski Nautique, GT40


Posted By: boo
Date Posted: March-10-2012 at 9:30pm
Gordon,

My 2002 SN GT40 has the same problem. We used the Star Tester to extract fault codes from the engine's computer and the codes were all 11 which indicated the systems were fine.

The next procedure the manual recommends is to check the fuel pressure regulator and the vacuum system. Today we connected the fuel pressure gauge at the wash ramp. (We ski in saltwater.) By the time we pull the boat out of the water and drive to the wash ramp the engine has cooled down enough to have the idle problem. It was unbelievalbe that the engine didn't lope. Tomorrow, we'll be connecting the gauge again.

I have a thread going on Planet Nautique and have yet to have anyone some up with a solution.

Sincerely,
Tom T.

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Tom T.
2002 SN GT40


Posted By: 8122pbrainard
Date Posted: March-10-2012 at 9:38pm
Originally posted by boo boo wrote:


I have a thread going on Planet Nautique and have yet to have anyone some up with a solution.

Sincerely,
Tom T.

PN?
Tom,
You have got to be kidding me!!! Is that site sill around? If so, do you really expect a technical question being answered? Give me a break!! The only reason the site is still on the web is because it is corporate sponsored!!!   

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54 Atom

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64 X55 Dunphy

Keep it original, Pete
<


Posted By: 63 Skier
Date Posted: March-10-2012 at 9:42pm
I have pretty much the same problem on my Sport, will be tackling the problem in a month or so, so this thread could be really helpful to me!

It didn't give me any trouble when skiing, but definitely at hot idle and a few times after near open throttle runs.

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'63 American Skier - '98 Sport Nautique


Posted By: slmskrs
Date Posted: March-11-2012 at 4:16am
Originally posted by <br />By the time we pull the boat out of the water and drive to the wash ramp the engine has cooled down enough to have the idle problem. .[/QUOTE
By the time we pull the boat out of the water and drive to the wash ramp the engine has cooled down enough to have the idle problem. .[/QUOTE wrote:




My theory is that it is heating up, not cooling down. With then engine off, there is no flow of air, so the air surrounding the engin


My theory is that it is heating up, not cooling down. With then engine off, there is no flow of air, so the air surrounding the engine gets hot (even without the blower on, then engine pulls a lot of air through the bilge). Also, if I've been having the problem, if I open the engine compartment when I know I'll have to start it in 20-30 minutes when it would definitely lope with then cover closed, it won't lope but will run fine,

Therefore, since it gets hotter, maybe there is some vaporizing of gas somewhere, such as in the fuel rails, at the regulator, etc.

Murphy's Law it didn't lope for you today. I probably won't have my boat back in the water for 3-4 days, but will try to remember to take the pressure gauge with me to test it as well.

Where do you ski (salt water)?


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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: March-11-2012 at 4:40am
Originally posted by 63 Skier 63 Skier wrote:



It didn't give me any trouble when skiing, but definitely at hot idle and a few times after near open throttle runs.


NEVER happens for me during normal operation; only at hot start up when it has sat for a while. Once I give it some throttle to keep it running and once it settles down, there is no problem whatsoever.

Actually, as I write the above, I'm starting to think about the ISCV again, simply because by opening the throttle, it runs better. If the ISCV is having an issue, opening the throttle would "cover up" that problem.

Of course opening the throttle could also cover/mask the source of other problems as well. I wonder if there is a way to get data on the operation of the ISCV if fuel pressure is okay since I have no idea how to test it.

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Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: March-11-2012 at 9:11am
Gordon I am chasing a similar problem on my GT40 Sport. It is a heat related problem also. The intermittent problem I have is when turning the engine off after a run it will not restart like normal with no throttle. After you crank it a few times you then have to hold the throttle wide open and clear the flooded condition. It can take up to 2-3hrs of running before the problem surfaces.   

Sometimes the idle will fluctuate just before it happens which makes me suspect the ISC-BPA solenoid. I have found if the engine is not turned off between runs the problem never happens. This is a bit weird but the ISC-BPA could just be sticking when it gets hot due to a weak solenoid. So when the power is reapplied to the solenoid on restart it fails to operate. The more you turn the engine over without it starting the more fuel that will be dumped into the cylinders. This is why it exhibits a very flooded condition on restart and requires the full open throttle to restart.

I also purchased a ford code reader but it had no fault codes stored for KOEO,Continuous or KOER tests. The EEC does not store a fault code for the ISC-BPA so it is still a suspect.

I have previously cleaned and tested the ISC-BPA. Yesterday I removed the ISC-BPA assy from the engine again. You can see the solenoid actuate when you turn the key on and off. This is a good test for proving the correct operation of the ISC solenoid. The engine was warmed up when tested but not for the 2-3hrs it can take for the problem to exhibit. I also found that with the ISC-BPA removed the engine will start and run with a slightly higher idle. I plan to use this as a test to eliminate the ISC-BPA as the cause of the problem next time it occurs. By removing the ISC assembly you allow airflow behind the closed butterfly via the now open port.

It could also be a ACT,ECT or MAP sensor but I should have had a stored fault code for those items.

Will let you know the outcome via this thread. I hope this gives you some where to start looking yourself.

-------------
If you're going through hell, keep going

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Posted By: eric lavine
Date Posted: March-11-2012 at 11:32am
the temp sender can also heat up and send false info to the computer, when its warmed up this may overfuel because the senseor is telling the engine it is still cold...i believe there are 2 sensors, one for the gauge and one for the computer

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"the things you own will start to own you"


Posted By: boo
Date Posted: March-11-2012 at 12:04pm
Gordon,

Regarding the ISC-BPA, the manual states if the valve is bad, upon rapid deceleration there would be an idle problem. That makes sense becuase the throttle body butterfly valve closes completely and the ISC-BPA needs to open to allow air around the butterfly valve for idle purposes. I don't have that problem and it sounds like you don't either.

Today, we're skiing again and will put the fuel pressure gauge on the fuel rail at the wash rack. If we can't duplicate the idle loping again today, then I will test the boat tomorrow evening after work when the engine is totally cold.

We ski in San Diego.

Stay tuned, I'm determined to troubleshoot this issue until it's resolved. I forgot to mention that the fuel pressure yesterday, when the engine would no lope, was 34 psi, which is within limits at proper idle. At idle it should be 31 plus or minus 3.

Tom T.

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Tom T.
2002 SN GT40


Posted By: slmskrs
Date Posted: March-11-2012 at 3:09pm
Originally posted by lewy2001 lewy2001 wrote:

I also purchased a ford code reader but it had no fault codes stored for KOEO,Continuous or KOER tests. The EEC does not store a fault code for the ISC-BPA so it is still a suspect.


Is the connector a ODBII? If so, where is it? I have an ODB reader (although for this problem, as you said, there are no error codes. But it would be nice to diagnose other issues.

[/QUOTE]
You can see the solenoid actuate when you turn the key on and off. This is a good test for proving the correct operation of the ISC solenoid........ I also found that with the ISC-BPA removed the engine will start and run with a slightly higher idle. I plan to use this as a test to eliminate the ISC-BPA as the cause of the problem next time it occurs. By removing the ISC assembly you allow airflow behind the closed butterfly via the now open port.[/QUOTE]

Great info!! I will try removing the ISC-BPA (for my car it's called an ISCV) and then starting it when it has the problem. Only issue will be doing it fast enough that it doesn't cool too much with then engine cover open so that it runs normally.

One word of caution when it is flooding the engine. I was helping jump a friend's carburetted SN. She has poor/corroded jumper cables (we were doing this at the launch ramp (no dock) from my car). Because the cables were poor, we could get it to barely turn over, but it wouldn't start. Of course she was pumping the throttle, etc. We finally pulled the battery out of her truck, disconnected the dead one, connected the new one. With her in the boat and me on the ramp holding the boat (luckily with the engine cover closed), she then started it. A very loud bang, the engine cover jumped up. We opened the engine cover, and all of the fuel vapor while trying to start had collected in the exhaust pipe/muffler, and blew out the side of the fiberglass muffler! We were lucky the cover was closed! So please be careful if it is acting flooded!!!

Let us know how your tests go. Between all of us, we should be able to figure this out!

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: March-11-2012 at 3:16pm
Originally posted by eric lavine eric lavine wrote:

the temp sender can also heat up and send false info to the computer, when its warmed up this may overfuel because the senseor is telling the engine it is still cold...i believe there are 2 sensors, one for the gauge and one for the computer


You are correct; on the GT40 (at least my '96), there are two temperature sensors. There is one on the forward side of the starboard intake manifold just aft of the thermostat housing. This has two wires that go to it. One goes to the dash gauge and I don't know where the other one goes other than in a harness to the rear of the engine. There is another sender in the circulation pump housing that also goes to the rear. I have not pulled the one in the circulation pump to see if it is a temperature sender or some sort of pressure sender ).   At least you can tell if the one on the intake manifold is working since it is connected to the gauge, but I have no idea what the other wire is for. I assume the one on the pump is for the EMC, but I will have to dig around for a wiring diagram to see where that other lead goes on the manifold sender.

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: March-11-2012 at 3:28pm
Originally posted by boo boo wrote:

Gordon,

Regarding the ISC-BPA, the manual states if the valve is bad, upon rapid deceleration there would be an idle problem. That makes sense becuase the throttle body butterfly valve closes completely and the ISC-BPA needs to open to allow air around the butterfly valve for idle purposes. I don't have that problem and it sounds like you don't either.

Today, we're skiing again and will put the fuel pressure gauge on the fuel rail at the wash rack. If we can't duplicate the idle loping again today, then I will test the boat tomorrow evening after work when the engine is totally cold.

We ski in San Diego.

Stay tuned, I'm determined to troubleshoot this issue until it's resolved. I forgot to mention that the fuel pressure yesterday, when the engine would no lope, was 34 psi, which is within limits at proper idle. At idle it should be 31 plus or minus 3.

Tom T.


Tom, I don't have the deceleration problem either.

I will have to check to see if my pressure gauge hose is long enough that I could put it on and have it laying on the floor with the engine compartment closed. That way I don't risk it cooling enough to have the problem not happen (like what happened to you yesterday). Hopefully you'll be able to get it to lope when flushing it today.

If your test is successful and it shows constant pressure, then I'm going to do what Mark suggested and have a socket wrench all ready to very quickly remove (or at least break the seal) on the ISC-BPA since that's a great test as well. It may not be until next weekend until I have conditions that will cause it since it's cooling down this week.

Mission Bay!! I hooked up with a couple of members probably 8-10 years ago while on a business trip, took my ski and got a ride on the course there (I'd have to dig around to get their names). If you are ever in the SF bay area, we're www.sccwsc.org and I'd be happy to give you a pull. Same to you Mark although you are a bit farther away than Tom.... :-(

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Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: March-11-2012 at 11:19pm
Originally posted by slmskrs slmskrs wrote:

Is the connector a ODBII? If so, where is it? I have an ODB reader (although for this problem, as you said, there are no error codes. But it would be nice to diagnose other issues.


It is on the bracket that supports the computer it is a black plug marked with EEC Test. My tester is a OBD1, MCU for Ford Engines.

Eric there are 3 water temp sensors on the GT40 engine.

1. The ECT sensor near the front on inlet manifold it is a two wire device as it has a signal return to the EEC. This is the main one for controlling fuel and ignition via computer.

2. Engine temperature gauge sender

3. Engine temp switch that puts the EEC computer into limp(SLOW) mode

The ECT (engine coolant temperature) is used to control the fuel delivery the others are not. The ACT air charge temperature is near the ECT mounted into the side of the inlet manifold it is also used to control fuel delivery. I have not ruled them out but they should have returned a fault code.

I recently changed my FCC filter and checked fuel pressure. I have also not ruled out the fuel pressure regulator as it may be over pressuring as it has a too rich problem.

-------------
If you're going through hell, keep going

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Posted By: boo
Date Posted: March-12-2012 at 12:26am
Gordon,

Yesterday, I connected a fuel pressure gauge to the valve on the fuel rail. Started the engine on the wash rack. This was after a morning of skiing and the engine had cooled down during the twenty minute ride from the water to the wash ramp. The engine idled perfectly. This has never happened in the last six months. It always has the loping idle and then it would eventually stall.

This morning, I launched the boat with the fuel pressure gauge connected to the fuel rail valve. Started the boat and it idled perfectly. This has never happened in the last six months, either. The fuel pressure at idle was 34.5 psi. The manual specification is 31 psi plus or minus 3 at idle. Unfortunately, I was not able to check the fuel pressure with the idle loping symptom present.

After skiing for 3 hours today, I trailered the boat to the wash ramp. Started the boat to flush the engine and the loping idle was present. (The gauge was not connected.) Conclusion, connecting the gauge removed the symptom and the engine idled perfectly both times the gauge was installed. Why? I don’t know yet. Was there air in the system that the gauge’s hose bled out? If so why does it only happen when the engine is cold? Why does it go away by turning the engine off and then on again?Not sure but I will go back to the manual’s Pinpoint Test section and proceed with more tests.

Keep in mind that the engine runs perfectly except for the first start upon launching the boat and after it has sat for about 30 minutes. Stay tuned. I will fix this problem.

The course on Mission Bay now has boat guides and turn balls that self adjust up and down with the tide. One of our members invented the stainless steel pulley system. It's absolutely unbelieveably superb. In 2006 we built a new dock, too.

Tom T.


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Tom T.
2002 SN GT40


Posted By: boo
Date Posted: March-12-2012 at 12:40am
To All,

Regarding the ISC-BPA, on page 3D-11, Step 3-Output Cycling Test, states operation of EEC controlled engine actuators can be performed at the conclusion of the KOEO self-test when using the Star Tester. I didn't do this test because I felt my Idle Speed Control-Bypass Assembly was okay.

Tom T.

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Tom T.
2002 SN GT40


Posted By: slmskrs
Date Posted: March-12-2012 at 4:12am
Originally posted by boo boo wrote:



This morning, I launched the boat with the fuel pressure gauge connected to the fuel rail valve. Started the boat and it idled perfectly. This has never happened in the last six months, either.

After skiing for 3 hours today, I trailered the boat to the wash ramp. Started the boat to flush the engine and the loping idle was present. (The gauge was not connected.) Conclusion, connecting the gauge removed the symptom and the engine idled perfectly both times the gauge was installed. Why?

Keep in mind that the engine runs perfectly except for the first start upon launching the boat and after it has sat for about 30 minutes. Stay tuned. I will fix this problem.

The course on Mission Bay now has boat guides and turn balls that self adjust up and down with the tide. One of our members invented the stainless steel pulley system. It's absolutely unbelieveably superb. In 2006 we built a new dock, too.

Tom T.


Tom,

I only get the cold start loping when it is really cold (like air in the low 40s. Otherwise I don't get it (so don't get it very often--a few times this winter).

Okay, your results are just plain weird! :-) On the surface, I'd just call it a coincidence, as it really doesn't make sense.....or does it? What if there is some sort of pressure surge. But when the pressure gauge is hooked up, there is not only the length of a hose that can expand and contract slightly with pressure, but there is definitely air in that hose, and you will compress that air so that when whatever is causing the pressure to drop, the air expands, keeping the pressure from dropping as much as it would without the hose, and maybe it is just enough to keep it from loping?

I'd love to see you duplicate and see if the test results are repeatable. Since it appears that you get cold start loping every time (whereas I only get it when it is really cold), you could try starting it without the gauge connected. If it starts to lope, immediately shut it off, put the gauge on, and restart (I have tried shutting off and restarting a cold loping engine and it doesn't make it better).

So, just thinking out loud if I had the same results, I think I'd do the following (depending on how frequently you are using it, you could do a few tests over a couple of days):

Day one: Start cold, if loping, shut off, quickly put gauge on and restart. If loping stops, either shut off immediately, take gauge off and restart, or wait and do day two test.
Day two: Start cold, if loping, shut off, wait the same amount of time it took to put the gauge on (but don't put it on this time), and restart. If loping stops, the waiting period is what stopped it. If it keeps loping, then attaching the gauge stopped it.

Do you ever have the problem while out at the course when it is warm? If I'm pulling back to back skiers with only a 5-10 minute stop, I never have a problem. But if we are boat rotation (max three boats allowed at a time) so I wait for two skiers or 20-30 minutes when the air is warm, it lopes. If you have the same scenario, you could do a number of similar tests the same day between boat rotations. But if not, then it looks like your only hot engine test is when you are at the flushing station. I will make sure to have my gauge when I go out next time and if it is warm enough, I'll do these tests as well.

It's not cold enough for me to get the cold start loping so I can only work on hot engine loping. For that to happen, the air needs to be at least in the 70s (at least when it happened Saturday, it was around 70 outside).

We're on a percolation pond here in San Jose, But with rain and the water district playing around with the dam, we can fluctuate upwards of 18 inches. We have sub-floats with 3 or 4" diameter capped PVC tubes with a cylinder lead weight with a stainless cable; the cable coming out of a hole in the top. The weight appropriately counterbalances the buoy and has about a 12" travel (depending on how deep or shallow it is at the anchor). It works reasonably well, but we don't have the daily level change you guys have. I was course caretaker a number of years ago and even though the deepest is only about 12', I dove with tanks many times to do repair (visibility on a good day is about 2", usually around a foot). What is the average spread between high and low tides there? When I skied there, you still had the old dock. I told your club president at the time (I skied with him and someone else and I'm pretty sure it was a Nautique) that he and anyone in the club had an open invitation for a pull up here and no-one has taken me up on it yet......

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: March-12-2012 at 5:07am
Just had to run out to give my youngest daughter's boyfriend a jump. Probably corrosion rather than a bad battery, but his battery is behind the rear seat, so I wasn't going to get out a hydrometer, etc. to check (just jumped to a positive terminal in the engine compartment).

Anyway, while I was driving back from giving him the jump, I though of another possible test to run when it is loping (at least a hot loping test since it seems that the causes of hot and cold loping would be completely different).

When the key is turned to ignition, both pumps go on for a half second or a second unless the engine is starting/running. However, there is a terminal on the test port that you can jump to turn the pumps on (I did that when testing the flow rate of my low pressure pump last year). I've always thought the hot loping was caused by some vaporizing somewhere and you needed some time and RPMs to get cooler fuel into the rails (in other words, the FCC isn't perfect). So another test for loping would be to jump the pumps and let them run for a minute or two before starting (simulating the flow of fuel during the first minute or so of loping). I would think that would flush enough cooler fuel through the system that if there was a vapor issue, it would be resolved (since running it at higher throttle runs more fuel).

Again, it seems that loping is caused by erratic idle speed control valve behavior, but if it is a fuel/pressure issue, I'd probably try this as an additional loping test.

Of course, I don't want to have to jump the pumps every time, but that would help to narrow down the search for the source of the problem.

Dang! I need my weekend extended so I can work on this!

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Gordon '97 Ski Nautique, GT40


Posted By: boo
Date Posted: March-12-2012 at 12:36pm
Gordon,

Please check your Private Message Inbox.

Tom T.

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Tom T.
2002 SN GT40


Posted By: boo
Date Posted: March-13-2012 at 3:06am
The boat sat yesterday afternoon and all day today. After work today, I drove to the boat and connected the garden hose to the engine’s flush connection. Instead of connecting the fuel pressure gauge to the relief valve on the fuel rail, I did something different. I unscrewed the relief valve’s cover and used a small flat tip screwdriver to depress the valve’s stem - just like you would release air from a tire if you overinflated it.

I placed my ear very close to the valve as I depressed it very, very gently with the screwdriver hoping I might hear some air flow out of it. I did not hear any air. I removed the screwdriver from the valve tip so it would spring back closed and then threaded the cover over the relief valve.

Next, I started the engine. It idled up perfectly for about 5 – 6 seconds and came down to its proper idle speed. In other words, the engine idle loping did not occur. I’m definitely onto something. The engine never should have idled properly after putting it away yesterday when it loped on the wash ramp. Every time I’ve depressed that valve stem, the next time I start the engine it idles perfectly.

For now, this will be my last post until I figure out why pressing the relief valve on the fuel rail causes the engine to idle correctly on a cold start. The cause is probably a vacuum leak. I will find it if that’s the culprit.

I’m not a mechanic so what I’m about to say please consider the source. I do not know how long it takes for the fuel rail pressure to subside, so pressing the relief valve, I would assume, could produce catastrophic consequences if its still under pressure. Something like an explosion or fire.

With 900 views to this thread, I hope I’ve helped some of you with my postings. So far, I’m very happy with the results. My next post may take weeks or months but I will post the final outcome.

If any of you have been able to temporarily resolve your idle issue using this method, please post it here. I would like to know.

Tom T.


-------------
Tom T.
2002 SN GT40


Posted By: slmskrs
Date Posted: March-13-2012 at 4:32am
Originally posted by lewy2001 lewy2001 wrote:

So when the power is reapplied to the solenoid on restart it fails to operate. The more you turn the engine over without it starting the more fuel that will be dumped into the cylinders. This is why it exhibits a very flooded condition on restart and requires the full open throttle to restart.


Just a quick thought. If the idle speed solenoid is failing to open upon hot start and therefore little air is getting mixed with the fuel, if you cracked the throttle slightly to let air in, then it should start rather than just dumping fuel into the cylinders with no start (it would just immediately start racing). Just wanted to check to see that it is not starting when you crack the throttle (at the start, not when it is already "flooded"). If it start when the throttle is cracked open, then it is the solenoid (or something in the line (low voltage, etc.)). If it doesn't start if you crack the throttle at the beginning, then I don't think it is the idle valve solenoid.

Just a thought....

-------------
Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: March-13-2012 at 4:36am
Originally posted by boo boo wrote:

I removed the screwdriver from the valve tip so it would spring back closed and then threaded the cover over the relief valve.

Next, I started the engine. It idled up perfectly for about 5 – 6 seconds and came down to its proper idle speed. In other words, the engine idle loping did not occur.


That is just plain weird! :-) I can't test it since it just isn't cold enough form my boat to have cold start loping (funny since it is always warmer in San Diego than here near San Francisco). So I can only test hot loping (assuming it is warm enough this weekend), but I will definitely try bleeding the rail (with a rag or something so I don't blow up) and see if that stops the loping.

-------------
Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: March-13-2012 at 9:27am
Originally posted by slmskrs slmskrs wrote:

Just a quick thought. If the idle speed solenoid is failing to open upon hot start and therefore little air is getting mixed with the fuel, if you cracked the throttle slightly to let air in, then it should start rather than just dumping fuel into the cylinders with no start (it would just immediately start racing). Just wanted to check to see that it is not starting when you crack the throttle (at the start, not when it is already "flooded"). If it start when the throttle is cracked open, then it is the solenoid (or something in the line (low voltage, etc.)). If it doesn't start if you crack the throttle at the beginning, then I don't think it is the idle valve solenoid.

Just a thought....


Yep that would be a valid test. I will try that next time it happens as a fault finding option.



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Posted By: SNobsessed
Date Posted: March-13-2012 at 10:54am
Originally posted by lewy2001 lewy2001 wrote:

The intermittent problem I have is when turning the engine off after a run it will not restart like normal with no throttle. After you crank it a few times you then have to hold the throttle wide open and clear the flooded condition.

Lewy - believe it or not I occasionally have this problem on my carb'd '89.

I just deal with it as you explained. must be the nature of the beast!

-------------
“Beer is proof that God loves us and wants us to be happy.”

Ben Franklin


Posted By: lewy2001
Date Posted: March-13-2012 at 11:07am
Chris that is the one of the benefits with fuel injection perfect idle hot or cold. Normally best if you leave the throttle alone and let the computer do all the adjusting of mixture and timing. Until something goes wrong.

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Posted By: 63 Skier
Date Posted: March-13-2012 at 12:00pm
My experience with having to open a throttle fully on hot starts (on carb'ed engines) is that the problem is generally caused by ignition, not fuel. Weak spark caused by coil, wrong plugs, wrong gap, etc. is something to look at in that situaion, plus timing.

-------------
'63 American Skier - '98 Sport Nautique


Posted By: SNobsessed
Date Posted: March-14-2012 at 12:29am
I have a pretty good ignition system, I think that maybe the needle doesn't seat right & lets extra gas flow into the bowl.

I wonder if the FI loping could be a leaky injector?

-------------
“Beer is proof that God loves us and wants us to be happy.”

Ben Franklin


Posted By: slmskrs
Date Posted: March-14-2012 at 12:36am
Sounds like a personal problem :-) , but I believe there are some tests on the injectors in the troubleshooting guide; I suspect I will eventually go through those tests as well (there are about a bazzilion possible causes for what they call "rolling idle"), going to have to plod through a lot of stuff (although some don't make sense, such as blocked fuel filter--you can't run at WOT with no problem and then have a fuel filter cause loping for 60 seconds on start, etc.). So I will pick and choose some of the tests I do. We will find the problem eventually. Too bad PCM is no help; it seems that most of the people there now haven't been there long enough to know what a GT40 is (9 years ago?).

-------------
Gordon '97 Ski Nautique, GT40


Posted By: gun-driver
Date Posted: March-14-2012 at 12:48am
I don't understand what you mean by loping???
Is it idling high than low/up and down like surging.


Posted By: Bohinny
Date Posted: March-14-2012 at 12:57am
My 1995 SNOB GT 40 has the hard start and rolling idle so please post any solutions cuase I sure have not figured it out.

-------------
Billy


Posted By: slmskrs
Date Posted: March-14-2012 at 2:11am
Originally posted by gun-driver gun-driver wrote:

I don't understand what you mean by loping???
Is it idling high than low/up and down like surging.


Surging. Up and down, up and down, about a about a 3 second cycle. It will get worse and worse, and half the time it will finally drop low enough that it stalls. The manual apparently refers to it as a rolling idle.

-------------
Gordon '97 Ski Nautique, GT40


Posted By: Stone_ld
Date Posted: March-28-2012 at 9:44am
Well, playing role as mechanic is very tuf as repairing of vehicle is not so easy task. As to repair this engine loping is also very difficult, for it http://www.rankmymechanic.com/" rel="nofollow - auto mechanics plays an important role and there are many online reviews for it.



Posted By: slmskrs
Date Posted: March-28-2012 at 4:56pm
We've had rain the past two weekends and it's supposed to rain on Saturday. I need a few warm days to have the correct environment for the engine to lope when hot. I have my fuel pressure gauge and a vacuum gauge already connected so I can see what they are doing when it happens. I'll post again when I have some results or move further along in the diagnostics.

-------------
Gordon '97 Ski Nautique, GT40


Posted By: M3Fan
Date Posted: March-28-2012 at 6:31pm
Wow, all I can say is I'm damn impressed with what you guys have come up with so far- lewy and slmskrs especially. Great work so far. I have nothing to add, but I'm staying tuned because this is a really interesting thread!



-------------
2000 SN GT40 w/99 Graphics/Gel
2016 SN 200 OB 5.3L DI
https://forum.fifteenoff.com






Posted By: lewy2001
Date Posted: March-29-2012 at 8:59am
Guys went out the weekend and after 2hrs of hard running turned the boat off and sure enough no restart. Tried to restart with some throttle and then removed ISC assy. Still no start the only way to get a restart was max throttle it would restart and run rough until it cleared. I have now ruled out the ISC-BPA. With max throttle the throttle position sensor would probably have been signalling the computer to apply max duty cycle to the injectors making it harder to clear the rich condition.

Plugged the code reader in and found a continuous stored code 15 (Power interruption to EEC computer). Removed 60 pin plug from computer and found some oxidised pins. Cleaned them roughly but a proper clean would need to wait till boat was back on dry land with correct cleaning agents. It restarted but it had probably a 30-45 mins to cool down with the engine cover raised.

It is looking like a heat soak problem with a bad high resistance connection some where. Although this is the first time it has had a stored error code. Maybe the problem is getting worse though.

After some research and investigating found that the EEC has it's own power wire run directly from the battery. It has a 50 amp inline fuse also in the battery enclosure. Always wondered where that extra power wire from the battery terminal went. This power wire runs back to the 12.5 amp cct breaker on the EEC computer bracket then to the EEC relay also mounted on the EEC bracket. The RHS relay when viewing from the rear is the EEC power relay the LHS relay is the fuel pump relay. The EEC power relay supplies power to pins 37 and 57 of the EEC connector. Interestingly it also supplies power to the fuel pump relay activation circuit. The EEC then supplies the ground to complete this circuit and start the fuel pumps. The 15 amp cct breaker on the EEC bracket is the power source for the fuel pumps.

I cleaned up all the contacts but did not find any real bad connections that may have been causing the problem. The 60 pin connector had a couple of pins with white deposits but nothing really substantial. I had a spare relay so I have replaced the EEC relay with it as the HR joint may have been inside the relay. Will see how this goes on next trip out. Will take my voltmeter along with the code reader.


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Posted By: M3Fan
Date Posted: March-29-2012 at 12:11pm
Lewy, just as an FYI there was a service bulletin (?) released a while back which eradicates that extra power wire and inline fuse. Essentially the power is instead wired directly to the fused side of one of the push breakers above the engine computer. That inline fuse in the battery compartment is a common source of GT40 problems but I always thought it went to the fuel pump relay. Learn something new every day! I can snap a pic of my wiring on that bracket if you want as I had the fix done by the dealer.

-------------
2000 SN GT40 w/99 Graphics/Gel
2016 SN 200 OB 5.3L DI
https://forum.fifteenoff.com






Posted By: east tx skier
Date Posted: March-29-2012 at 7:43pm
I'd love to see a picture of the wiring, Joel. Mine still has the fuse. My understanding is that you do a couple of jumpers on the breaker panels. Do you lose the wire to the battery altogether?

I haven't had problems with the fuse. But by removing it, I would never have problems with it.

-------------
http://correctcraftfan.com/diaries/details.asp?ID=2383&sort=&pagenum=7&yrstart=1996&yrend=2000 - 1998 Ski Nautique (Red & Silver Cloud); GT-40; Perfect Pass Stargazer; Acme 422.





Posted By: lewy2001
Date Posted: March-29-2012 at 9:00pm
Joel would also like to see the pictures or original bulletin. It does seem a complicated way of powering the EEC when there already is the main battery cable located right there on the power assist solenoid.

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Posted By: M3Fan
Date Posted: March-29-2012 at 10:10pm
Here you go. You can see the wire tied to the fused side of the 60A breaker (with yellow eyelet crimped on). Now, in my boat's case since I have the electronic dash this wire goes forward to the On/Off/Bilge toggle switch that the electronic dash boats have.



-------------
2000 SN GT40 w/99 Graphics/Gel
2016 SN 200 OB 5.3L DI
https://forum.fifteenoff.com






Posted By: east tx skier
Date Posted: March-30-2012 at 1:19am
Thanks, Joel. I think I have someone lined up to do the fix for me for lunch and some beer.

-------------
http://correctcraftfan.com/diaries/details.asp?ID=2383&sort=&pagenum=7&yrstart=1996&yrend=2000 - 1998 Ski Nautique (Red & Silver Cloud); GT-40; Perfect Pass Stargazer; Acme 422.





Posted By: lewy2001
Date Posted: March-30-2012 at 9:57am
Joel where is the on/off/bilge toogle switch located in the engine bay or up at the dash?

If I was to rewire mine I would run a 6-8 gauge wire from the main battery cable terminal on the power assist relay to the 12.5 amp breaker. This small run of wire less than 1 foot would replace the current wire from the battery box to the 12.5 amp breaker.


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Posted By: M3Fan
Date Posted: March-30-2012 at 10:34am
Originally posted by lewy2001 lewy2001 wrote:

Joel where is the on/off/bilge toogle switch located in the engine bay or up at the dash?




Up at the dash in my case. The switch cuts off all systems in the boat including the push-button/keyless dash which is a parasitic load on the battery. Relevant only to the 2000+ "smartpod" boats but probably not terribly unlike the ignition breaker on the older boats.

I remember when I went to test-drive this boat they still had the positive lead with the inline fuse at the battery. It gave us trouble on the test drive so the dealer I bought it from explained the fix to me and had it done before I brought the boat home.

Just took another look at the wiring and my 12.5 breaker is definitely unmolested. Both connections on it are still plasti-dipped from the factory. Both wires on the 12.5 run neatly into the wiring loom, complete with the woven protective sheathing on them both. There's no way this fix involved that breaker directly in my case- could someone have messed with the wiring on your boat? If not, perhaps the unfused side of the 12.5 breaker is powered via the dash somehow and that's why the new wire on my boat goes forward. Donno.

The red wire with the crimped eyelet on the 60 amp breaker (in the picture) is the ONLY non-factory wire/connection on the whole thing FWIW, and it does go forward to the dash area on my boat.

-------------
2000 SN GT40 w/99 Graphics/Gel
2016 SN 200 OB 5.3L DI
https://forum.fifteenoff.com






Posted By: east tx skier
Date Posted: March-30-2012 at 5:57pm
My understanding of it is that the wire from the battery is eliminated entirely (not just replacing the wire with a fuse with another wire without one).

-------------
http://correctcraftfan.com/diaries/details.asp?ID=2383&sort=&pagenum=7&yrstart=1996&yrend=2000 - 1998 Ski Nautique (Red & Silver Cloud); GT-40; Perfect Pass Stargazer; Acme 422.





Posted By: M3Fan
Date Posted: March-30-2012 at 6:32pm
Originally posted by east tx skier east tx skier wrote:

My understanding of it is that the wire from the battery is eliminated entirely (not just replacing the wire with a fuse with another wire without one).


Correct. Hope I didn't suggest to the contrary.

-------------
2000 SN GT40 w/99 Graphics/Gel
2016 SN 200 OB 5.3L DI
https://forum.fifteenoff.com






Posted By: east tx skier
Date Posted: March-30-2012 at 6:38pm
You didn't. But I saw a reference to replacing the current wire with an unfused wire above and figured I'd chime in.

-------------
http://correctcraftfan.com/diaries/details.asp?ID=2383&sort=&pagenum=7&yrstart=1996&yrend=2000 - 1998 Ski Nautique (Red & Silver Cloud); GT-40; Perfect Pass Stargazer; Acme 422.





Posted By: slmskrs
Date Posted: March-31-2012 at 4:35am
Originally posted by lewy2001 lewy2001 wrote:

Plugged the code reader in and found a continuous stored code 15 (Power interruption to EEC computer).


What code reader do you use?

-------------
Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: March-31-2012 at 9:54am
This is the http://www.amazon.com/Equus-3145-Ford-Digital-Reader/dp/B000EW0KHW" rel="nofollow - Code Reader Gordon the book that comes with the code reader has a lot better run down of the fault codes than the GT40 manual in reference section.

Joel my wiring looks factory all the liquid insulation is still on all the breakers. Would be nice to see the PCM Bulletin that was issued it would clear up what was done.
There must be more to it than just that wire. Seems weird to run that wire back to the dash when the wire on that breaker already goes there via the 10 way harness connector. The wire from the inline fuse probably appears at the dash harness connector and they have done something under the dash with this circuit. I am leaving my inline fuse EEC wire standard at the moment to see if the fault has been rectified.

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Posted By: slmskrs
Date Posted: March-31-2012 at 1:41pm
Originally posted by lewy2001 lewy2001 wrote:

This is the http://www.amazon.com/Equus-3145-Ford-Digital-Reader/dp/B000EW0KHW" rel="nofollow - Code Reader Gordon the book that comes with the code reader has a lot better run down of the fault codes than the GT40 manual in reference section.
.


Thanks Mark. One question: Does it come with a cable to plug into the port on the GT40, or do I need to order an extension cord for it? I have a compter-based ODB++ reader and of course the plug for that looks nothing like the one on the GT40.

Thanks,

-------------
Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: March-31-2012 at 10:10pm
It plugs straight in the the EEC tester connector above the relays.



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Posted By: slmskrs
Date Posted: April-01-2012 at 9:42pm
Thanks! It's in my Amazon shopping cart! :-)

-------------
Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: April-21-2012 at 5:41am
Update had the boat out for four days over the Easter break. Put almost 20 hrs on the meter without the problem reoccurring. Looks like it was the EEC relay.

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Posted By: Bri892001
Date Posted: April-21-2012 at 1:24pm
Lewy, would you mine weighing in here with the problem and fix:
http://www.correctcraftfan.com/forum/forum_posts.asp?TID=25584&title=poor-mans-gt40-diagnosis" rel="nofollow - http://www.correctcraftfan.com/forum/forum_posts.asp?TID=25584&title=poor-mans-gt40-diagnosis

I can add a new row in the spreadsheet for EEC Relay.


Posted By: lewy2001
Date Posted: April-22-2012 at 11:21am
Brian you add the extra rows and I will update.

Looks like I need a new battery the Interstate has been in there since April 2004. Not bad, I can see why you US based people like these batteries.

While I had it out for testing and charging decided to check all the connections on the 50 amp EEC fuse circuit. Cut away the heat shrink from the fuse holder and found the crimped connections were still in good shape. Would prefer to see them soldered and a heavier gauge wire used. No way that wire was ever going to carry 50 amps over that distance to the breaker at rear of engine. But I doubt it draws much more than 10 amps considering the breaker it goes to is only 12.5 amps. Not sure why they would use a 50 amp fuse in the first place.

I will replace fuse holder at least. At the moment contemplating removing this circuit all together. Will chase this wire back under dash and see where it goes before ending up at the EEC 12.5 amp breaker. I will email Correct Craft and PCM and see if they can provide any info on retrofit mentioned previously that replaced this circuit.



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Posted By: slmskrs
Date Posted: April-22-2012 at 10:04pm
Just an update on the loping problem (since I started the thread). Now that we have had warm weather, it is hot start loping all the time with the following conditions:
1. Ambient air at least 75F (was 91 yesterday)
2. Engine hot (have pulled 2-3 sets in the course)
3. Boat sits with engine off for about 30 minutes with engine cover closed (while other two boats at course take their turn (boat rotation)). Gets quite hot (no air flow) in the bilge. If I rotate with only one other boat, then the 10-15 minute with the engine off is not long enough to cause the problem.

When engine is started, immediately starts loping, and most of the time it is severe enough that the engine stalls. The way to "resolve" it is to run the engine at a high idle (usually over 1,000RPM) for 30-45 seconds or so before dropping back to idle.

I have checked the ECM and there are no codes. I also have a fuel pressure gauge and a vacuum gauge on the engine. When it is loping, the vacuum pressure goes up and down (expected since the RPMs are going up and down). The fuel pressure goes up and down between about 32psi to about 37psi (also to be expected since as the vacuum changes, the pressure regulator will change the pressure).

What I expected to see is pressure dropping below minimum (32psi?) during loping, but it never did that, so it appears that the injectors are getting correct pressure at all times.

I have:
* cleaned the throttle plate
* cleaned the idle speed control valve
* run injector cleaner fluid through the fuel system
* Confirmed that the tube in the FCC is good (if it wasn't, I'd see low pressure)

At this point, I don't think it is related to fuel pressure, so the next thing is air.

I think the next thing I will do when the symptoms appear is to pull off the idle speed control valve (ISCV). Of course, that will make it run at a high idle (which might be the same as cracking the throttle slightly to rev at high idle, so that could mask if the ISCV is bad). But I might be able to look into the plunger in the ISCV when I first start the engine to see if it is moving open and closed. That would tell me if the ISCV is what is moving and causing the loping.

If so, the next thing would be to see if it is the ISCV or something before that. Does anyone know what voltage the ECM sends to the ISCV? I'm wondering if I could put a volt meter across the leads (when it is loping) and see if voltage is fluctuating.

Anyway, I'm getting lots of loping in these warm conditions, so will advise what I find out.




-------------
Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: April-22-2012 at 10:40pm
Gordon sorry about the threadjack

That sounds like a good plan for the ISCV. Pinpoint test 3E10 in the GT40 manual gives you all the voltage readings required. Some of the readings require a breakout box on the 60 pin computer connector. When I was testing mine I found it much easier to look at the operation of ISCV than measure the voltages. Although I was looking for a bigger problem than just the rolling idle.

Another possibility could be weak spark. If you prove you have air and fuel it may be the next place to look.

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Posted By: slmskrs
Date Posted: April-22-2012 at 10:58pm
Hey Mark, no worries. I'm just glad that you found your problem with no starting after hard runs. At least if that happened to me at the north end of the slalom course, it would just amount to rowing to the other end where the launch ramp is. I would NOT want to be way out on some big lake somewhere knowing that could happen. :-)

I did have a question for you. When you pulled the ISCV, you said it idled with a slightly higher idle. Do you remember about what RPM it idled at? And also, how much does the ISCV move when you turn the ignition on? I'm curious as to if it moves to a different position between hot and cold. I guess I'll pull it and see what it does when cold when turning on the ignition, and then try it again when it is hot. Next weekend the weather is going to be back to normal temperatures for this time of the year (low 70sF (21-22c) rather than the 90sF (34-35C) we had yesterday, so I may or may not have a loping problem next weekend.

-------------
Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: April-22-2012 at 11:06pm
Gordon I remember watching it actuate by just turning the key on and off. My engine always idles around 1000rpm for a short period on initial start before dropping back to 650-700rpm. The high idle is due to the ISCV being open. With the whole assembly removed the idle speed was just above the 1000rpm maybe 1100rpm from memory.

If I get a chance this week I will make a video of what mine does and you can then compare it's operation to yours.

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Posted By: slmskrs
Date Posted: April-22-2012 at 11:22pm
I'm a bachelor next weekend (wife and youngest daughter will be out of town), so it will be a Nautique orgy--tons of skiing, and all sorts of work on the boat (prop shaft alignment), replace heater core hot water circulation pump with bigger pump), pull analog tach (it bounces all over the place and when I slug it, it settles down so I figure there is something loose in it--don't care too much since I have Stargazer, but a couple of drivers haven't given it enough throttle to engage because sometime my analog tach can read 4k rpm when it is not up to 3k).

Anyway, hoping it is warm enough that it will lope since I can spend a lot of time at the pond playing around with it. My engine does the same thing (initial start idle around 1k rpm and then drops down to 650-700). It sounds like when the ISCV is wide open, it is around 1k and with it removed, it is a bit over 1k. I don't know if I'll get loping at 1k or not since cracking the throttle will keep it running (above loping RPMs) until it stops. But if the conditions are right and it starts loping, I want to immediately pull the ISCV off and restart the engine and see if 1). there is still any loping, and 2). whether the ISCV valve "lopes" (moves open and closed). I guess the other thing I could do is to manually block off some of the air flow with my thumb (after taking the ISCV off) to slow the engine down, and then see if it lopes at the normal "loping RPM" without the ISCV.

The next would be spark, but I don't know where I'll look for that. I guess I could put a timing light on one of the plug wires and see if a spark is always firing or not. But I'll do the ISVC tests first.

Good thing the boat runs great otherwise. And I can always avoid the problem by either opening the engine compartment when at the dock if the engine is going to be off for more than 15 minutes, or just skiing more (pulling someone every 15 minutes). So not a major problem, just annoying (and embarrasing when it is my turn to pull someone and it stalls when I'm trying to back up out of the dock....

-------------
Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: April-22-2012 at 11:45pm
Mark, if you are able to take a video, that would be great. But please don't go out of your way to do so.

Thanks,

-------------
Gordon '97 Ski Nautique, GT40


Posted By: lewy2001
Date Posted: April-25-2012 at 8:32am
Gordon got some work done on the boat today and managed to get some video of idle speed bypass solenoid. Not great quality but should give you something to compare.



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Posted By: slmskrs
Date Posted: April-25-2012 at 1:07pm
Originally posted by lewy2001 lewy2001 wrote:

Gordon got some work done on the boat today and managed to get some video of idle speed bypass solenoid. Not great quality but should give you something to compare.



That's PERFECT! You even plugged the port with your fingers to bring the idle down. That is exactly what I'll do. I know we wouldn't be able to see it in the video, but I assume you can see the valve close slightly after start (where the idle would normally go from around 1000 back down to normal idle speed).

Anyway, thank you so much for doing that. I really appreciate it. I'm really hoping it is warm enough this Saturday that it will lope so I can do that test!

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: April-30-2012 at 1:36pm
Wasn't warm enough to lope this weekend until we were pulling the last person (and the wind was coming up so we were in a hurry to pull them). So no chance to pull the ISCV.

Just curious, has anyone with the (hot) loping problem replaced their injectors (and still have the problem)? Someone on the dock mentioned doing that for his truck and it ran so much better. Don't think that would be it, so I'm curious if anyone has replaced theirs (where'd they get them, part number, etc.), and if so, do they still have the loping issue (something else to eliminate from the mix).

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: May-03-2012 at 3:45am
As an FYI, for any of you that haven't been following the "99 SN GT40 Fuel Supply" thread, what is interesting here is that AB has got a loping problem, but the source seems to be completely different. But listen to the loping sound. I'm trying to figure out if there is any correlation related to our cold start and hot restart loping issues. Here's the video he posted: http://www.youtube.com/watch?v=0hihpHcuNvY

What's weird with his situation is that the loping has the same type of frequency (RPM oscillation), except his fuel pressure gauge makes no sense, whereas mine does exactly what I would expect it to do, higher PSI when the vacuum drops with RPM drop, and goes back to around 32psi with higher RPM (and manifold vacuum).

Anyway, for any of you following this that didn't see this, it is interesting since it is a different kind of loping problem.

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: May-19-2012 at 7:17pm
Just an update.

I did two tests today. The first was to jump the fuel relay to ground so that the pumps stay on. The idea behind this was to run the pumps for about two minutes to see if the flowing fuel somehow cooled down (assuming it was hot fuel causing the loping). So when I knew it was going to lope (hot, sitting for a while with the engine cover closed, I jumped the pumps (I already had it wired so I could jump them without opening the engine compartment) and let them run for about two minutes. When I started the engine, I still got loping.

The second test was to take off the idle speed control valve and check two things: 1. See if the valve was moving back and forth (which would cause the loping), and 2. place my fingers over the ISCV air opening to slow the RPMs back down to idle speed and see if it would lope.

I did not see the iscv moving back and forth when I started it. And when I blocked the ISCV air port to slow the RPMs down, there was no loping.

The most interesting thing was after these tests. I put the ISCV back on, we finished packing up to leave. I went to get the truck, and my ski buddy idled the boat to the launch ramp. I found out afterward that when he started it to idle to the ramp, it was loping.

So, with the ISCV off, it did not lope (even when I blocked the air port to drop the RPMs to idle speed). However, when I put the ISCV back on and the engine was started five minutes later, it loped.

Based on that, I'm questioning the ISCV more now. I looked at the movement of the ISCV packed up to leave when I got home, and it appears to be a little jerky (not bad, but it wasn't super "smooth"). So I may try cleaning it again (I tried when I replaced the heads but didn't power the valve so it would open).

If cleaning doesn't help it, I'm wondering if I need to get a new one.

Anyone replace one, know how much they cost, and where you get them (haven't checked skidim yet)?

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: June-16-2012 at 10:28pm
HOT LOPING PROBLEM SOLVED!!!

It was the ISCV (or whatever everyone here calls it, in the car forum I'm on, it's the idle speed control valve). I pulled mine and checked operation, cleaned it out, etc. Seemed okay, but I couldn't get ride of the hot loping. I managed to find the exact replacement from RockAuto for 1/4 what the marine folks wanted (exact same PN, etc.) so figured I'd go ahead and get a new one. I checked its operation with the old one and they seemed to do the same thing. But I put the new one in anyway just to see. I've had the boat out about six times but it has not been too warm / didn't really have perfect storm conditions so no loping problem. So I didn't know if I fixed it or not, until today. Today was the perfect storm. Mid 90s ambient, three boats in the pond (we only allow three at a time and we do boat rotation). When it is hot and my boat sits hot for 20-30 minutes (while the other two boats take their sets), I have always gotten loping, all the way to stalling. Anyway, hot, lots of the boat sitting around and going through the course every 30 minutes or so for some 5 hours. But it never loped. The idle might have been a tad rough (I think that is just a hot fuel issue), but idle never fluctuated more than 25RPM or so.

I wasn't sure that was the solution until today, when with the old ISCV it would have been loping like mad, stalling, etc..

I'm a VERY happy camper and can finally close this thread!!!!

Thanks to everyone for all of their input, etc. Especially to LEWY; he took great video of the ISCV and let me know that I could run the engine with it off, etc. That helped a lot. Also to TomT in San Diego, who has documented his loping (and not loping) for probably 25 outings.

Happy Nautique'ing everyone! It's gonna be a great summer!!

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Gordon '97 Ski Nautique, GT40


Posted By: slmskrs
Date Posted: June-16-2012 at 10:38pm
BTW, I can't seem to edit the GT40 spreadsheet, so here's the info:
IACV PN: e9se9f715eb (off the original valve)
http://www.rockauto.com/catalog/moreinfo.php?pk=945342
$55.79 + shipping

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Gordon '97 Ski Nautique, GT40


Posted By: Luchog
Date Posted: June-17-2012 at 2:38pm
2nd and 3rd post first page...

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http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique

Commander 351W


Posted By: slmskrs
Date Posted: June-17-2012 at 3:36pm
Great Point!! Agreed it was mentioned up front. I pulled the valve immediately when I got that info, cleaned it, checked operation, which seemed normal. Problem remained but only with those specific conditions. Pulled it again, cleaned it again (while opening and closing it), watched video of others with it, confirmed movement was the same. Wasn't any obvious problem with the operation, so in order to not to just start throwing parts at the problem to see what sticks, I did a lot of other checks, tests. In the end the valve was the problem and the only way to tell was to put a new one in. And of course there were other suggestions which I also followed, so while I now wish I had just replaced it at the beginning, I know my pumps, pressure regulator, etc. are all working well, I learned a lot more than I previously knew about the system, and hopefully this thread with all of the various suggestions, etc. will help others hone in on the problem (whether it be the valve, the pressure regulator, pump, relay, ECC, etc.).

Also, I was able to source a much less expensive valve (which is why it made it easier to just go buy one and try it. :-)    I'll spend $60 to try something, but hesitant to spend $225 or more when I can't tell if it is bad or not. So I'll do more checking first. :-) Anyway, again, thanks to everyone for the suggestions, etc.

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Gordon '97 Ski Nautique, GT40


Posted By: Bri892001
Date Posted: June-18-2012 at 12:38pm
Great you fixed it! I'll edit the spreadsheet with this information.


Posted By: 1994nautique
Date Posted: July-14-2012 at 2:27am
Is this on a port fuel injection or throttle body?


Posted By: slmskrs
Date Posted: July-14-2012 at 4:22am
Multi port fuel injection.

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Gordon '97 Ski Nautique, GT40


Posted By: boo
Date Posted: August-17-2015 at 11:06pm
Finally the solution has been discovered. Our local independent boat mechanic connected a fuel pressure gauge to the fuel rail and then proceeded to use a C-clamp and slowly squeezed the fuel pressure regulator until the fuel pressure reached its maximum tolerance.

It's been 6 months since he "squeezed" the fuel pressure regulator and the oscillation has only occurred twice and not bad enough to turn the engine off and then on again. The idle evened out on its own.

In all fairness to the Nautique dealer, crushing the fuel pressure regulator was one of the options he recommended back in 2012 at the time of my first post. It was my choice to leave it as the last viable option. It turned out to be the solution.

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Tom T.
2002 SN GT40


Posted By: slmskrs
Date Posted: August-18-2015 at 1:12am
Originally posted by boo boo wrote:

proceeded to use a C-clamp and slowly squeezed the fuel pressure regulator until the fuel pressure reached its maximum tolerance.


Any pictures of how you squeeze the fuel pressure regulator? Not understanding how it is done, and what it is actually doing. But interesting/inexpensive (unless you squeeze a little too hard.... :)

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Gordon '97 Ski Nautique, GT40


Posted By: Luchog
Date Posted: December-11-2015 at 7:49pm
When you restrict the return line, pressure on the rail increases


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http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique

Commander 351W


Posted By: curiouslibra
Date Posted: January-13-2018 at 6:30pm
The symptoms this thread is describing are so exactly what my 1999 air Nautique gt-40 is doing that I’ve ordered the part from your link without troubleshooting anything else from the boat. I had buxton marine in Lewisville work on it when I first got the boat. They claimed that the aftermarket headers that the previous owner put on when they did the engine overhaul is what is causing the rolling idle. I just assumed I had to live with the problem as everyone previously states if you get rpm above 1200 it quits doing the hunting or if I shut off the motor and start it back up it idles fine. Also it seems like the computer gets into a feedback loop that gets worse until it dies once it starts hunting for idle. The price for the part is now down to $43! For that price its cheaper than paying for them to troubleshoot this problem any further. If this cures it I’ll report back to this thread to give more people with is situation more confidence this is the fix. I’ll also tell their mechanic they could learn a few things from this site and I’ll owe you a beer if we ever meet in person!

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W
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l
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"Don't argue with idiots, onlookers will not be able to tell the difference between the two of you, as the idiot drags you down to their level and beats you with experience."


Posted By: 8122pbrainard
Date Posted: January-13-2018 at 6:53pm
Originally posted by curiouslibra curiouslibra wrote:

I had buxton marine in Lewisville work on it when I first got the boat. They claimed that the aftermarket headers that the previous owner put on when they did the engine overhaul is what is causing the rolling idle.!

Don't you love it when a dealer with so called trained "techs" can't come up with a better excuse for not knowing what's going on!!

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/diaries/details.asp?ID=1622" rel="nofollow -

54 Atom

/diaries/details.asp?ID=2179" rel="nofollow - 77 Tique

64 X55 Dunphy

Keep it original, Pete
<


Posted By: Luchog
Date Posted: January-13-2018 at 8:30pm
please post the link to the IAC valve so it can be added on the GT40 spreadsheet topic

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http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique

Commander 351W


Posted By: Peter6000
Date Posted: January-14-2018 at 2:28pm
I had the same problem on my 1999 GT40, started after I had the engine rebuild due to a crack in the block.
I chased it for about 1 year without success. I did all the above listed suggestions.
I also intensely checked ignition system, valves, vacuum and fuel injectors all looked normal.
I finally broke down and decided to get to the bottom of the problem and installed 2 oxygen sensors in the exhaust system using adapter plates.
My measurements showed a AFR of 14.5 to 15.5 when the idle was looping.
Doing some research specially in some mustang forums that is way to lean for batch fire fuel system.
On of the mustang guy's blamed it on the overhauled engine, the higher displacement would need more fuel.
To prove the point I installed a fuel pressure regulator with adjustment screw.
Now I upped the fuel pressure (about 2-4 psi) my AFR went to 12.5 and the Idle problem was gone.
Doing some further testing I found out that my this caused also a to lean mixture at high RPM and a hot start issue due to lean mixture on hot start up.
Over all adding a little less fuel pressure got it actually running fairly descend.
This is all about 2 years ago.
I m a bit of perfectionist and did not like it. The stock ECU computer cannot really be manipulated so decided to replace it with a aftermarket MS3X.
I just got the installation finished I changed from batch fire to full sequential and from distributor to coil on plug.
Now I can tune any setting I like and match it to any situation.
So fare I have only tuned the idle its to cold to go on the water. But its incredible I can get it to idle ad 600 rpm perfectly stable.

.



Posted By: gt40KS
Date Posted: January-15-2018 at 11:52pm
Originally posted by Luchog Luchog wrote:

please post the link to the IAC valve so it can be added on the GT40 spreadsheet topic


Rockauto link:

http://www.rockauto.com/en/parts/airtex/wells,4J1024,idle+air+control+(iac)+valve,6072

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JCCI
1995 Ski Nautique GT40


Posted By: gt40KS
Date Posted: January-15-2018 at 11:56pm
Direct links:

http://www.rockauto.com/en/parts/airtex/wells,4J1024,idle+air+control+%28iac%29+valve,6072" rel="nofollow - Rockauto link:



http://www.rockauto.com/en/parts/motorcraft,CX1826,idle+air+control+%28iac%29+valve,6072" rel="nofollow - Motorcraft Brand:

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JCCI
1995 Ski Nautique GT40


Posted By: tryathlete
Date Posted: January-16-2018 at 1:12pm
Originally posted by Peter6000 Peter6000 wrote:

I had the same problem on my 1999 GT40, started after I had the engine rebuild due to a crack in the block.
I chased it for about 1 year without success. I did all the above listed suggestions.
I also intensely checked ignition system, valves, vacuum and fuel injectors all looked normal.
I finally broke down and decided to get to the bottom of the problem and installed 2 oxygen sensors in the exhaust system using adapter plates.
My measurements showed a AFR of 14.5 to 15.5 when the idle was looping.
Doing some research specially in some mustang forums that is way to lean for batch fire fuel system.
On of the mustang guy's blamed it on the overhauled engine, the higher displacement would need more fuel.
To prove the point I installed a fuel pressure regulator with adjustment screw.
Now I upped the fuel pressure (about 2-4 psi) my AFR went to 12.5 and the Idle problem was gone.
Doing some further testing I found out that my this caused also a to lean mixture at high RPM and a hot start issue due to lean mixture on hot start up.
Over all adding a little less fuel pressure got it actually running fairly descend.
This is all about 2 years ago.
I m a bit of perfectionist and did not like it. The stock ECU computer cannot really be manipulated so decided to replace it with a aftermarket MS3X.
I just got the installation finished I changed from batch fire to full sequential and from distributor to coil on plug.
Now I can tune any setting I like and match it to any situation.
So fare I have only tuned the idle its to cold to go on the water. But its incredible I can get it to idle ad 600 rpm perfectly stable.

Impressive technical solution. Wish you lived next door. Interesting to see the AFR variance and lean condition at higher RPMs. That’s detonation waiting to take down an engine if you ask me. Worst way to go. Takes all sorts of valuable parts down with it. I’m assuming you’ve done as mentioned (LPP/HPP/plastic clear tube/ IAC/MAF....).

.



Posted By: Peter6000
Date Posted: January-18-2018 at 1:44pm
Detonation is always a concern, that's why my next step is to add 2 knock sensors for early warning. However the MS3X can run closed loop and has a emergency shut off system to prevent killing the engine while tuning.
I started a post on my conversion If somebody is interested I can post all my findings.
http://www.correctcraftfan.com/forum/forum_posts.asp?TID=42211
And yes i tried all these LPP/HPP/plastic clear tube/ IAC/MAF no luck.
Peter



Posted By: KENO
Date Posted: January-18-2018 at 5:04pm
Originally posted by Peter6000 Peter6000 wrote:

Detonation is always a concern, that's why my next step is to add 2 knock sensors for early warning. However the MS3X can run closed loop and has a emergency shut off system to prevent killing the engine while tuning.
I started a post on my conversion If somebody is interested I can post all my findings.
http://www.correctcraftfan.com/forum/forum_posts.asp?TID=42211
And yes i tried all these LPP/HPP/plastic clear tube/ IAC/MAF no luck.
Peter



I'd put it all in one thread, say the one you started.

It might be good to link the posts by some guy with the same name from the Megasquirt support forum into that thread too

Good info and pictures in those posts


Posted By: curiouslibra
Date Posted: January-27-2018 at 2:27am
Ok I finally got the IACV in the mail and went to put it on and noticed the wire that connects the IACV also connects to this black thing on top of the throttle body that has wires going to it and has a circular hole that I don't know if there is a piece missing from the hole or if this is normal and should look like it does. I'm hoping one of you experts on here can tell me what this is and if this is normal on a GT-40 engine or if I'm missing a piece that is suppose to go into that hole?






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W
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l
l

"Don't argue with idiots, onlookers will not be able to tell the difference between the two of you, as the idiot drags you down to their level and beats you with experience."


Posted By: Gary S
Date Posted: January-27-2018 at 9:21am
Yes your missing a piece. I'll bet you can't buy it separately. That is the throttle position sensor. Must be adjusted if you replace it too, you'll have to look that up.

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http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS
95 Nautique Super Sport


Posted By: Gary S
Date Posted: January-27-2018 at 9:36am
http://imgbox.com/EQfUkJIP" rel="nofollow">

http://imgbox.com/QA7GTTAJ" rel="nofollow">

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http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS
95 Nautique Super Sport


Posted By: curiouslibra
Date Posted: January-27-2018 at 4:56pm
I checked for a new throttle position sensor and the new ones don't have a cover on them either! Since the boat has been running fine except for the looping that the IACV should fix, I'm going to hold off on getting anything for the TPS until I test the motor with the new IACV. I was just shocked to see an opening on the top of the manifold when I took off the cover.

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W
i
l
l

"Don't argue with idiots, onlookers will not be able to tell the difference between the two of you, as the idiot drags you down to their level and beats you with experience."


Posted By: 63 Skier
Date Posted: January-27-2018 at 9:17pm
I don't understand how a GT-40 could run without a TPS.

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'63 American Skier - '98 Sport Nautique


Posted By: Luchog
Date Posted: January-27-2018 at 9:23pm
Originally posted by 63 Skier 63 Skier wrote:

I don't understand how a GT-40 could run without a TPS.


of course it isnt, he's being missleaded.

Will, go ahead with the IAC valve, forget about the TPS for the moment.

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http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique

Commander 351W


Posted By: curiouslibra
Date Posted: January-28-2018 at 12:44am
One more question. The iacv came with a new gasket there isn’t a packaging film I have to take off is there? One side has lettering on it while the other side is just plain gray and uniform in color. Does it matter which side goes toward the iacv?

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W
i
l
l

"Don't argue with idiots, onlookers will not be able to tell the difference between the two of you, as the idiot drags you down to their level and beats you with experience."


Posted By: Peter6000
Date Posted: January-29-2018 at 2:26am
The TPS is still there its only the top cover that is missing, I don't think that would create a problem unless its a vacuum leak easy to test run in idle and cover the hole with your finger if you feel suction or the idle changes it is a problem.
If replace it you need to adjust it as mentioned earlier the procedure is in the Pro Boss manual. You need a multi meter to do it.



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