1994 Chevy S-10 Idling extremely high...

[dyankee1995]

1994 Chevy S10, 4.3L, V6, 170,000 miles...

The motor idles extremely high even when it is warmed up.

I cleaned the idle air control motor. I cleaned the throttle body inside and out. There are no vacuum leaks. If I remove the idle air control motor and adjust the length to make the seat longer, it will idle normally. But, over a period of about a month of driving, it will drive itself back open causing the same problem.

What can be causing this reoccurring problem? Could it be an engine temperature sensor?

Thanks,
David B.

[old_master]

I would suspect a sticky IAC motor or a carbon build up on pintle seat for the IAC in the intake manifold.

[dyankee1995]

Originally Posted by old_master

I would suspect a sticky IAC motor or a carbon build up on pintle seat for the IAC in the intake manifold.

I suspected it was a sticky IAC motor. It seems like it will drive open but not closed.

Thanks for your help.

David B.

[old_master]

The IAC is actually a "stepper motor" meaning it is extended and retracted in "steps" by the ECM. The ECM can calculate what position the pintle is by how many "steps" it commanded. If the seat is carboned up, or the pintle slips on the motor shaft, the ECM has know way of knowing what position the pintle is in. The gear in the IAC is nylon and the motor shaft is steel and it can strip the threads in the gear and become out of sync.

[dyankee1995]

Originally Posted by old_master

The IAC is actually a "stepper motor" meaning it is extended and retracted in "steps" by the ECM. The ECM can calculate what position the pintle is by how many "steps" it commanded. If the seat is carboned up, or the pintle slips on the motor shaft, the ECM has know way of knowing what position the pintle is in. The gear in the IAC is nylon and the motor shaft is steel and it can strip the threads in the gear and become out of sync.

Wow! Thanks for the quick response...very helpful!

David B.

[j cAT]

Originally Posted by dyankee1995

Wow! Thanks for the quick response...very helpful!

David B.

If you adjust the IAC the plastic gears are damaged ....this should not be adjusted ....

this engine has vacuum line issues use a vacuum guage to check all vacuum lines ...especially lines on the tbi/intake manifold area..