Idle Speed/Throttle Actuator - Electronic: Description and Operation

CIRCUIT DESCRIPTION
The Idle Air Control (IAC) valve is situated on the intake air chamber. Intake air bypassing the throttle valve is directed to the IAC valve through a passage.

A step motor is built into the IAC valve. It consists of four coils, a magnetic rotor, valve shaft and valve. When current flows to the coils due to signals from the Engine Control Module (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.