IMPOSSIBLE High Idle- tried everything HELP! - Third Generation F-Body Message Boards

JWeidner89 · 11-02-2009, 03:37 PM

Alright I've never posted something here so bear with me, I'll try to be specific as possible. I have a 89 Camaro with a 350 crate engine, about 20k miles. Last week I washed the engine, and covered up all the basics. When I was done washing the engine, the car was idling high (about 2k) then an hour later it wouldn't start. Figured out that the Throttle position sensor was keeping it from starting (would unplug TPS and car starts right up) so I put a new TPS in. Car still idling about 2k though. The problem is that when the car is shut off, the IAC opens, and when it is started back up, it is not closing. My mechanic hooked up his computer to it and manually ran the IAC down, the car then Idles and drives 100% perfect (right at 750 rpm) until the car is shut off and turned back on, then it immediatlely idles high and will not come back down. Mechanic said it has got to be the computer, the Hypertech prom chip, or a sticking IAC. I bought a new computer, put the stock PROM chip back in, and put a new IAC in to no avail. Same exact problem every time. Mechanic thinks the wiring is good because he can run the IAC up and down at will with his diagnostic tool. Turning the Idle screw down does nothing even when you force the throttle shut. And I dont think it can be a Vaccum leak because when the iac is set back down, the car runs perfect. Please let me know your thoughts, it's really killing me. so in short THE IAC IS STICKING OPEN EVERY TIME THE CAR IS SHUT OFF AND RE-STARTED. WHEN IAC IS MANUALLY ADJUSTED THE CAR WILL RUN PERFECT UNTIL IT IS SHUT BACK OFF. agh.. . . .

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NINÅ · 11-03-2009, 03:07 PM

If the ECM is receiving incorrect coolant temperature information it can cause that type of problem.

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