Idle Air Control Motor

Idle Air Control (IAC) motor is mounted on throttle body. It is an electric stepper motor. The Powertrain Control Module (PCM) adjusts engine idle speed through the IAC motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air by-pass passage that provides air for the engine during closed throttle idle. The IAC motor pintle protrudes into the air by-pass passage and regulates air flow through it. The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the by-pass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, manifold absolute pressure sensor and various switch operations (brake, transmission range sensor and air conditioning). When engine RPM is above idle speed, the IAC motor is used for off-idle dashpot, deceleration air flow control and A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine RPM does not dip down when the compressor engages).