Idle Speed/Throttle Actuator - Electronic: Description and Operation

PURPOSE
Controls engine idle speed--preventing stall due to changes in engine load.

OPERATION
- If RPM drops below a specified RPM and the throttle plate is closed, the ECM will sense a near stall condition, calculate a position--based on barometric pressure--and actuate the IAC to prevent stalling.

The IAC assembly, mounted on the throttle body, provides the ECM control of bypass air around the throttle plate by extending or retracting a conical valve to divert air around the throttle plate.
- If RPM is lower than desired more air is passed around the throttle plate to increase RPM.
- If RPM is too high, less air is diverted the throttle plate to decrease RPM.
At idle speeds, the ECM calculates the desired position depending on battery voltage, coolant temperature, engine load and engine RPM.