What would cause my car to idle for example 700 rpms and as u walk away from your car it jumps up to 1200 for no reason
what part makes it do that



thanx nick

 

Theres lots of variables that effect Idle, but ultimatly its the IAC (idle air controller) that has mechanical control, as it allows air to pass by the butterflys.

 

It is possible that the ECM is going from closed loop to open loop, and back. This can happen on an idling engine if the exhuast temperature is not high enough to maintain an adequate O² sensor signal. That can cause variation in idle, as well as any unknown variables in the HyperScrap PROM you have installed.

As C1500 said, the IAC is the ultimate controller of idle speed, so it and the air passages must be kept clean to have accurate idle control.