Idle Air Control

Air Intake System Diagram:

PURPOSE

The Idle Air Control (IAC) valve is opened by current controlled by the Engine Control Module (ECM) to change the amount of air bypassing the throttle valve to the intake manifold to maintain a proper idle speed.
A Fast Idle Thermo Valve is employed to provide additional air for a fast idle at low coolant temperatures.

OPERATION

- After the engine starts, the IAC valve opens for a certain time. The increased air raises the idle speed by 150 - 300 rpm.

- At low coolant temperatures, the Fast Idle Thermo Valve opens to allow air to pass into the intake manifold to obtain the correct fast idle speed. As coolant temperature increases, the valve closes to maintain the proper idle speed.