Idle Air Control (IAC) Motor

The IAC motor is mounted on throttle body and is used by the PCM to adjust engine idle speed. The throttle plate regulates off-idle engine speed by controlling the amount of air allowed to enter the intake manifold, and is mechanically operated by the accelerator cable.

The PCM and IAC motor adjust engine idle by regulating the size of an air by-pass passage that routes air past the closed throttle plate. The amount of air flowing through the by-pass circuit depends on engine operating conditions at idle.

When the engine is cold, the PCM increases engine speed by retracting the IAC motor pintle, thus allowing more air to enter the intake manifold. To maintain the proper air/fuel mixture, more fuel is also injected into the intake manifold. The increased air/fuel mixture, in turn, raises the engine idle speed. As the engine warms, the PCM will extend the motor pintle into the air passage to reduce the amount of air by-passing the throttle plate.