Idle Speed/Throttle Actuator - Electronic: Description and Operation

IAC Motor Circuit:

PURPOSE
The Idle Air Control (IAC) servo maintains idle speed by compensating for loads placed on the engine.

OPERATION
As the motor rotates, as determined by the ECM, the plunger extends or retracts. Intake air passes through the plunger opening and idle speed is controlled bypassing this air around the throttle blade.

The Idle Air Control (IAC) servo adjusts the idle for air conditioning and automatic transmission loads, anti lock braking, and is used as a fast idle for cold start. The ECM uses the Idle Speed Control (ISC) servo to make idle adjustments.

CONSTRUCTION
The (IAC) servo consists of a motor, worm gear, worm wheel and plunger. A position sensor is used to detect plunger position and a closed throttle position switch is used to detect idle position. The worm wheel (attached to the motor shaft) is meshed with the worm gear on the plunger.