GT40 engine loping |
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Peter6000
Newbie Joined: June-04-2017 Location: Northern VA Status: Offline Points: 25 |
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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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curiouslibra
Newbie Joined: January-10-2018 Location: Dallas Texas Status: Offline Points: 26 |
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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." |
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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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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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4229 |
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I don't understand how a GT-40 could run without a TPS.
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'63 American Skier - '98 Sport Nautique
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curiouslibra
Newbie Joined: January-10-2018 Location: Dallas Texas Status: Offline Points: 26 |
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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." |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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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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curiouslibra
Newbie Joined: January-10-2018 Location: Dallas Texas Status: Offline Points: 26 |
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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
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." |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10606 |
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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 |
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Peter6000
Newbie Joined: June-04-2017 Location: Northern VA Status: Offline Points: 25 |
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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 |
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1796 |
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gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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JCCI
1995 Ski Nautique GT40 |
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gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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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 |
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Peter6000
Newbie Joined: June-04-2017 Location: Northern VA Status: Offline Points: 25 |
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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. . |
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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please post the link to the IAC valve so it can be added on the GT40 spreadsheet topic
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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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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curiouslibra
Newbie Joined: January-10-2018 Location: Dallas Texas Status: Offline Points: 26 |
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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
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." |
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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When you restrict the return line, pressure on the rail increases
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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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
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boo
Newbie Joined: January-25-2012 Location: San Diego, CA Status: Offline Points: 20 |
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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 |
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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Multi port fuel injection.
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Gordon '97 Ski Nautique, GT40
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1994nautique
Newbie Joined: March-21-2012 Location: Wyoming Status: Offline Points: 29 |
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Is this on a port fuel injection or throttle body?
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4945 |
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Great you fixed it! I'll edit the spreadsheet with this information.
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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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
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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2nd and 3rd post first page...
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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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
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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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
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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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
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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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
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slmskrs
Gold Member Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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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
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