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Re: IAC maybe?
Try stopping vacuum on the hose going to the brake booster.
If the booster gets a torn diaphragm in it, excessive vacuum will be flowing, and it creates a vacuum leak.
We did a lot of diagnostics on one of the boards recently and the problem was the booster.
Check for other vacuum leaks too.
An engine coolant sensor failing or with a bad connection can make the ECM think the engine is cold and the ECM will speed up the RPM.
The IAC could be getting bad.
Sometimes when the distributor gets worn, the shaft wobbles around, and the ECM gets a poor RPM signal for controlling the idle speed.
How’s that for a few ideas!
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For those of you that are wondering why you are not getting replies to your thread:
Did you give the model, year, engine, fuel system type, and transmission information?
If it is modified from what came stock from the factory, let us know that too.
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