GT40 intermittent idle problem

[boo]

When my 2002 Ski Nautique's GT40 engine is cold, sometimes the idle occilates up and done and will almost stall. I then turn the engine off and then on again. Usually the idle returns to normal. The fuel pumps are new. The throttle body is very clean. The distributor cap, rotor, wires, and plugs are new.

Has anyone experineced this symptom? If so, were you able to correct it and how?

Sincerely,
Tom T.
San Diego, CA

[jimmyj]

have the same problem in my 2001 off and on, except mine happens when the engine is hot and sits for a few minutes, like in between riders or stopping and talking to somebody.

you can search on here and it seems to be a somewhat fairly-ish common issue on the gt-40s. from what i have read, can be a number of things, including the throttle position sensor, idle air control valve, 12v fuse coming from battery....

mine is intermittent. had my boat for 5-6 years now. have had entire summers where it didnt happen once, and then this past summer is happened quite regularly. might try and address it this year. when it starts happening, i simply turn the boat off and right back on again, like you were saying.

know this doesnt really help you too much, but just wanted to comment so you know you are not the only one.

i have noticed that when mine is doing it, my volts are low and fade in a out with the surge in the idle. probably somewhere from 10-12.5 volts while the engine is surging. i need to upgrage my alternator to handle the current load i put on the battery. seems that this may could cause the issue, but doesnt really explain why the engine never does it when its cold, unless the higher rpms when cold keep the engine from doing it. typically when it happens, idle will flucuate from 200 - 800+ rpm.....

[mdvalant]

2000 Sport with a GT40 and notice this on occasion. I would compare it to more of a surging and almost stalls. Funny thing, I have the 5.0 in my explorer and it does the exact same thing at stop lights sometimes but will actually stall out. Both motors do it when they're warm/have been working hard.

[stp900]

1997 GT40 owner here and last summer had the exact same issue. Cold starts would produce the bouncing RPM's and often times stall. Once the engine was warm it ran perfectly. Once I stopped the boat for more than a few minutes, the cold start problem would happen all over again until it was warmed up. I trouble shot it all last summer doing the following in order: replaced the 2 relay switches, low pressure fuel pump, then replaced the Idle air control (make sure you spend the money and buy the PCM one, not the Ford counterpart...did not work for me). Finally what fixed it completely was the Throttle Position Sensor. I got it fixed in time for only one more run on the lake before storing it for the winter. It did fix the problem and now she starts everytime and the idle is right at 650 RPM's with no bouncing at all. What a difference it makes when launching your boat....imagine you just start it once and it stays running perfectly!!! Anyway, hope this helps.

[mrbobolina]

TPS is going to be your challenge 90% of the time when talking about odd idle when cold which goes away when warm. Intermittent issues are 9/10 going to be a bad ground. Do not be fooled into thinking that because the bolt is tight the ground is clean. Depending on the salinity of your lake, you will get some salt film on those bolts. That soft white haze. In other cases it may be rusted. The best is the rust under paint, or people who try to ground to a painted surface. Check your ground and that will be the culprit.

For the TPS - if you do not replace it, at some point you will end up stranded on the water.

[Chexi]

Unfortunately, there are many possible causes of your problem. I had an idle problem (with stalling) after my boat warmed up (so opposite of you). I tried swapping out the TPS, the MAP, checking and cleaning grounds, new plugs, new wires, new distributor new TFI... none worked. Finally I had the distributor replaced, which solved the problem. I suspect it was just the PIP inside the distributor, but it now works, and I have a host of parts for when those other items go.

Murhpy's law ensures that intermittent problems will not manifest themselves when your boat is at the dealer. So, if you can video the problem and post a link here (and/or send to your trusted mechanic), it would probably help a lot.

[boo]

Thanks to all that replied. You've helped tremendously. I will keep you posted on the outcome. Quite a few more items to check before I purchase parts. Would really like to narrow it down to what is actually malfunctioning. This may take several weekends.

[mrbobolina]

Boo - this will help you to test the tps. http://www.youtube.com/watch?v=IsX5q3jBeBQ

Cold idle challenges that go away when warm are TPS most to the time. This testing process will help make sure.

[boo]

I hope I'm adding to my original post correctly. Tom T here again from San Diego. I've been reading my PCM PRO Boss GT-40 EFI Diagnostic Manual. My engine has an EEC-IV (electronic engine control) Self Test Input and Output connector. When connected to a Star Tester, it's supposed to reveal fault codes for the ACT, ECT, PIP, MAP, and TFI-IV sensors/circuits. It will not signal a faul code for the AIC. The ECA (computer) holds fault codes for 40 engine temperature cycles. This sounds too good to be true. As soon as I find someone that has a Star Tester, I will post the results.

When my 2002 Ski Nautique's GT40 engine is cold, sometimes the idle occilates up and done and will almost stall. I then turn the engine off and then on again. Usually the idle returns to normal. The fuel pumps are new. The throttle body is very clean. The distributor cap, rotor, wires, and plugs are new.

Has anyone experineced this symptom? If so, were you able to correct it and how?

Sincerely,
Tom T.
San Diego, CA

[gtxragtop]

I bought one of these for my 1996 Ski Nautique GT40. Not because I have any issues but it is cheap enough to have on hand.
I plugged it in and code 11 came up.. All tests passed.
http://www.amazon.com/gp/product/B00...00_i01_details

[jeffkuk]

Would this work on a 1998 fi gt-40? It says obd 1. Are these later ones still obd 1? Also is this as good as star tester? can it give specific fault codes or will it just say fuel system for example? Thanks a lot!

[boo]

Thank you for the link to the tester. I'm going to investigate the price and availablity of the Star Tester part number 007-0041B from the manual. You're right, it will be a good investment to have in my tool box.

I'll keep everyone posted on the outcome.

[gtxragtop]

Compatible only with MCU and the EEC-IV computer control systems. If you have a EEC-IV computer, it works. I do not have the details on when or if the GT40 engine moved to a different computer. Yes, it gives you a code and the manual that comes with it has an extensive list of codes and descriptions.
Here is a link to the GT40 service manual. http://www.correctcraftfan.com/Downl...ice_Manual.pdf

[boo]

Boo here again with my lastest update. EBayhas Star Testers for sale. One is model 007-0041 and one is model 007-0041A. Since the manual stated the "B" version must be used, I've decided to call the manufacturer Hickok for their feedback. They are still in business located in Ohio.

[crashman]

TPS is going to be your challenge 90% of the time when talking about odd idle when cold which goes away when warm. Intermittent issues are 9/10 going to be a bad ground. Do not be fooled into thinking that because the bolt is tight the ground is clean. Depending on the salinity of your lake, you will get some salt film on those bolts. That soft white haze. In other cases it may be rusted. The best is the rust under paint, or people who try to ground to a painted surface. Check your ground and that will be the culprit.

For the TPS - if you do not replace it, at some point you will end up stranded on the water.

Hi I'm new here- just picked up a 2001 closed bow SN with the GT-40. Can you tell me where to look for the ground wire? Thanks!