99 chevy malibu 6 cyl auto, idle speed too high sometimes 2500 rpm, Sometimes will go back to normal if I shut the car off and restart, sometimes not, Sometimes will be ok on start and increase after car is driven. Mech says possibly caused by defective pressure sensor on the power steering?
Has the IAC (Idle Air Control) valve been checked/cleaned?
The power steering pressure sensor tells the computer when the power steering system puts a load on the engine. The computer then adjusts the engine idle speed via the Idle Air Control motor to compensate for the extra load imposed on the engine. But I’ve never heard of this switch causing the engine speed to go too high. When they fail, the engine stalls anytime the steering wheel is turned while the accelerator isn’t being depressed.
The problem you describe sounds more like a problem with the Idle Air Control motor itself.
I’d be inclined to replace the idle air control too. Not very expensive and could be sticking from time to time. When starting, the computer sets the IAC for what it thinks is the right position but if its not it will be at high idle until you shut it off again and re-start it. Now I hate to say it but if its not the IAC, it could be a problem with the computer or wiring sensing the throttle position.