How hard should it be to manually pull out IAC plunger? Another high idle problem.

I've been trying to diagnose an intermittent high idle that occurs occasionally when warm. The odd time when I stop driving my idle sticks at 1100 rpm instead of the usual 750. If I put the truck in gear, apply the break, and release the clutch just enough to drop the engine rpm to about 500 and let the clutch out again it will idle back at 750. I was thinking maybe a sticky IAC stepper motor. I removed it and the only way I could manually move the plunger was to put the plunger in a vice and wiggle the IAC while pulling or pushing on it pretty hard.

By the way, TB is clean, O2 is new, IAT and Coolant temp sensors read in spec. TPS input 4.85V output .83V, MAP within spec. My base idle when warm (IAC fully closed and disconnected, throttle set screw adjusted for idle) is about 600 rpm.

Re: How hard should it be to manually pull out IAC plunger? Another high idle problem.

You are not supposed to push or pull the plunger due to the stepper motor design. If you moved it, there is a good change your fubar'd it. You are also not supposed to have it connected and powered when it is not in the vehicle. The computer can cause the motor to adjust beyond its normal limits and screw things up as well.

A high idle is normally caused by a vacuum leak rather than the IAC. On earlier Renix based units the leak is normally the hard line where it runs by the battery.

Bender said:

I removed it and the only way I could manually move the plunger was to put the plunger in a vice and wiggle the IAC while pulling or pushing on it pretty hard.

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You killed it now. Just get a new one, it's only $42.99 at autozone....