Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
does it idle normal?
have you cleaned the throttle plate and throttle body and iac?
these are info requests we have not finished the question.. any pending or history codes?
it sounds like a failed iac thats why I pointed you in that direction I don't want you just to throw parts at it
CIRCUIT DESCRIPTIONThe engine idle speed is controlled by the idle air control (IAC) valve. The IAC valve is on the throttle body The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is supplied current by two circuits from the powertrain control module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts with a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned OFF.First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed diagnostic trouble code (DTC) sets.DIAGNOSTIC AIDSInspect for the following conditions: