´96 Ford GT-40 with high idle........help!!!!

andy mogg

´96 Ford GT-40 with high idle, need help finding problem

I have a problem with the idle in my 96 Sport Nautique. Here´s what the problem is and what I have tried so far:

The problem started after the boat/motor being damp after some bad weather.(Don´t know if this has anything to do with the problem or not, just thought I should mention it) Took the boat out, and after the engine had been running for a while, the RPM´s went up to approx. 1800 when at idle. The condition got worse over a period of several months so that the engine would run at high RPM´s right after starting when the engine was cold. I have had the boat at 2 different mechanics that haven´t been able to find the problem. First they told me to replace the control unit, which didn´t help, and and we have also replaced the water temp switch and the water temp sender. Nothing has helped yet. Also, when the engine is running, if the water temp switch is removed or disconnected, the RPM´s will drop down to about 800, but not at a steady idle. (RPM´s rock back and forth slowly between 800 and 900)

Anyone ever have a similar problem or know where I should look next?

Thanks,

Lars

JUST-IN-TIME · Posted: Sep 04, 2008 12:25 pm Post subject:

is this FI or the crabed version?
might be iac valve

DRAGON88 · Posted: Sep 04, 2008 12:30 pm Post subject:

There was a "crabed" (sic) version of the GT40?

I thought the GT-40 (all of them) were TBI.

JUST-IN-TIME · Posted: Sep 04, 2008 12:48 pm Post subject:

i have seen one GT-40 carbed
i think it stopped in 1996

has the power pack on it and sensors, kind of weird

remember a GT-40 is just a stroked 351

scott a · Ladies Man Joined: 13 Jan 2003 Posts: 9810

I wouldn't stroke anything with crabs. Good luck with that.

DRAGON88 · Posted: Sep 04, 2008 3:32 pm Post subject:

JUST-IN-TIME, orly? The GT-40 is a stroker motor now? Laughing

Might want to double check on what the displacement is on that engine, because it is a 351.

JUST-IN-TIME · Posted: Sep 04, 2008 3:52 pm Post subject:

sheet, man im typed all fuct up today, lol

i meant 302!

JUST-IN-TIME · Posted: Sep 04, 2008 3:53 pm Post subject:

thanx for that!

K-dub · Ladies Man Joined: 12 Jan 2003 Posts: 14760

DRAGON88, he IS the certified mechanic....he "should" know that the Windsor is a 351.
I think he's "Stroker-ing" you.

JUST-IN-TIME · Posted: Sep 04, 2008 3:56 pm Post subject:

good one K-dub Mr. Green

DRAGON88 · Posted: Sep 04, 2008 3:56 pm Post subject:

Unfortunately I never really worked on the GT-40 when we had the Sport Nautique, but I would think since it is TBI it would have an idle adjustment screw somewhere on the throttle body area. Might also want to check to make sure the throttle linkage is not getting bound up.

JUST-IN-TIME · Posted: Sep 04, 2008 4:05 pm Post subject:

u can get the manual from planitnautque.com

they did make a carbed GT-40 motor, one guy on PN was just talking about it, then i remembered i worked on an old supra with it

bigkitch · Outlaw Joined: 16 Jan 2006 Posts: 161 City: Oakville

andy mogg,

the reason you get the rough idle when you disconnect the water temp sensor is most likely because the computer recognizes a sensor missing, and goes into a default setting. But since the other sensors are still reading, the idle will not stay constant.

I think you need to double check the temp sensor and sending unit again. It just sounds like the engine wants to run at a 'cold startup' setting and start screwing with the air/fuel mix.

Since its TBI, DRAGON88 is right in that there should be an adjustment for the throttle plate. Just double check that to make sure it has not gone out of wack for some reason. Also, with a TBI, there is no IAC valve which kinda eliminates that from the question, unless your running an efi setup. If it is an efi setup, i would bechecking that IAC valve.

Hollywood · Posted: Sep 16, 2008 10:27 am Post subject: