´96 Ford PCM GT-40 with high idle

´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

Sounds like a bad TPS sensor to me, our 96 super sport with GT40 had the exact same issues, swapped it out for $20 and it was perfect @ 650rpm again.

Rossl