Idle Speed/Throttle Actuator - Electronic: Description and Operation

PURPOSE

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

LOCATION

The IAC is located on the throttle chamber.

CONSTRUCTION

The (IAC) servo consists of a motor and shutter wheel. An IAC valve position sensor is used to detect shutter wheel position, and a closed throttle position switch is used to detect idle position.

Idle Air Control (IAC) Circuit:

OPERATION

As the motor rotates, according to the signal from the ECU, the shutter wheel opens or closes the size of the air bypass port. In this way, the idle speed is controlled by changing the amount of air bypassing the throttle plate.

The Idle Air Control (IAC) Valve adjusts the idle for air conditioning and automatic transmission loads and is used as a fast idle for cold start. The ECU uses the idle speed control (ISC) servo to make idle adjustments.