Idle Speed: Adjustments

The Vehicle Control Module (VCM) controls idle RPM with the Idle Air Control (IAC) valve. To increase idle RPM, the VCM retracts the AC pintle from the seat, allowing more air to bypass the throttle plate. To decrease RPM, it extends the IAC pintle valve in towards the seat, reducing air flow through the IAC valve port in the throttle body. A scan tool will read the VCM commands to the IAC valve in counts. The higher the counts, the more air allowed, or the higher the idle. The lower the counts, the less air allowed, or the lower the idle.