Idle Speed/Throttle Actuator - Electronic: Description and Operation

IAC Valve:

PURPOSE
The idle air control valve (IAC) maintains proper idle speed under various engine demand periods. The ECM directly controls operation of the IAC valve.

LOCATION
Mounted to the front of the air intake chamber.

CONSTRUCTION
The unit consists of a 4-winding stepper motor and a variable air passage.

OPERATION
When current flows to the coils due to signals from the ECM, the rotor turns and moves the valve shaft forward or backward, changing the clearance between the valve and the valve seat.

In this way the intake air volume bypassing the throttle valve is regulated, controlling the engine speed. There are 125 possible positions to which the valve can be opened.