When engine is started initially, the idling speed would be higher as the cold start system is commanded to increase the speed. As the operating increases, the cold start system would be disabled and this is when the idling speed would go down.
Under normal circumstances, the engine idling speed would be around 750 rpm and if idle air flow is reduced by restriction due to accumulated dirt inside the throttle body, especially around the area where the throttle plate closes, the idling speed would loer.
The IAC is not faulty, it is just dirty reducing the volume of air to pass through and lowering the idling speed.
You mentioned the car stopped 2 days ago, what was the problem? If the battery was disconnected, the engine computer needs to relearn and this would result in erratic idling with possibility of stalling. Some running would allow the computer to stabilise the idling speed and cleaning the throttle body and IAC would expediate the process. There are only good to be achieved by this process and no harm whatsoever.
Friday, October 12th, 2012 AT 1:10 PM