When I drive the ECM idles the car at 1500-2000 untill I stop or tap slightly on the gas. Sort of like a stuck throttle. I do not have a binding throttle or linkage. I replaced the TPS because it was not giving smooth increase. No change.
I also found the TPS sensor was rubbing on my Accel 58mm throttle body. Filed it down, no change.
Hooked up my scanner and the IAC (stepper motor) is ay 47-50 steps during the high idle, according to the book it should be 25 steps. This I think is causing the high idle. I am not 100% sure though.
What drives the IAC and why or when?
I am not along with this perticular problem, read other peoples comments and you will see. www.thirdgen.org/messgboa...00129.html



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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Heads, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine belt setup, Dual IROC Fans.

http://www.sethirdgen.org/octride.htm

 

Or a sticky IAC, or a vacuum leak (like a sticky EGR or EGR solenoid).. Or, a sticking throttle plate/shaft.

 

i had a high idle the other day and hooked up my scan tool, saw that the cts was reading 40 degrees f when it wasn't even that cold outside! Replaced the cts and everything is fine.

 

Guys this post I made was 5 years ago.

To answer the question i had it was a sticky throttle plate, an extra return spring solved it for good.

 

Better late than never.

 

I presumed you'd had it figured out by now, but just in case...