Idle Speed/Throttle Actuator - Electronic: Description and Operation

Idle Air Control (IAC) Valve Circuit:

Purpose:
The Idle Air Control Valve (IAC) valve controls the engine idle speed, prevents stalling due to changes in engine load.

Operation:
The IAC controls the amount of air bypassed around the throttle plate. This is actually a controlled vacuum leak. When more air is bypassed, idle speed increases, when less air is bypassed, the idle speed decreases. The IAC valve accomplishes this by moving a conical shaped pintle "IN" to decrease bypassed air and "OUT" to increase bypassed air. This can be seen as counts displayed on a "Scan" tool. Inward Movement of the pintle = Decreased RPM = Lower Counts. Outward Movement of the pintle = Increased RPM = Higher Counts.

Location:
The IAC valve is mounted to the throttle body.