Idle Speed/Throttle Actuator - Electronic: Description and Operation
IDLE AIR CONTROL MOTOR - PCM OUTPUTFig.16 Idle Air Control Motor Air Bypass Passage:
The Idle Air Control (IAC) motor is mounted on the throttle body. The PCM operates the idle air control motor.
The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes.
The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates air flow through it.
The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).