I have a 91 Sedan Deville, 4.6 Ltr.. When I turn the ignition key on, the Idle control motor also known as the Idle Speed Control, (ISC) runs all the way out then starts pumping the accelerator. After the engine starts, it start moving back in. When I shut the engine off, it runs back out and starts clicking again pumping the accelerator pedal.

Any one have any suggestions on how to fix the problem.

 

Hey Count: I have an 81 Brougham that had this same problem. I don't know for sure if the ISC is the same for your car, but mine is adjustable. Just adjust the screw that makes contact with the accellerator linkage, try a couple of screws turns out and then see if that corrects the problem and then try a couple in if no difference is noticed. You may have to adjust the idle screw after to get the idle speed back to where you want it. The pumping you describe is called throttle ratchet. Hope this helps.

 

I have removed the ISC from the car, and it still moves all the way out when the key is turned to "ON" and then slowly returns to original position once the engine is started. When it moves all the way out, it ratchets when it has travelled as far as it can.

So when I turn the engine ON, it ratchets out, then returns to normal. Then when I turn the engine off, it ratchets all the way out again.

I don't think it's the ISC at fault. I think it's a sensor sending a signal for it to extend out past it's limit.

I need someone that has a Shop manual with the wiring schematic for this circuit.

Thanks for the help.