The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows the necessary amount of air, as determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed.
Idle speed control is accomplished through the use of the Idle Air Control (IAC) motor or IAC valve in combination with ignition timing. Some applications use a second air passage and control device to provide additional air to compensate for the additional load created when the A/C compressor is running. The pintle-type IAC motor typically has a dual winding driven pintle that controls the size of a metered orifice that is part of the throttle body housing. The pintle seat will be at or near the axis of the throttle plate(s).