Vibe FWD L4-1.8L VIN 8 (2004)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
IDLE AIR CONTROL (IAC) VALVE
The idle air control (IAC) valve is attached to the underside of the throttle body with 4 bolts. The IAC valve enables the powertrain control module
(PCM) to easily control the engine idle speed by precisely metering the engines air intake at closed throttle. The AC valve opens and closes the idle air
bypass passage according to signals from the PCM. The IAC valve contains an engine coolant passage that enables the IAC valve to operate more
efficiently at cold temperatures. The PCM determines the correct engine idle speed by using input from various sensors and switches in order to assess
the engine status and requirements.
OPERATION
The PCM uses the IAC valve in order to control the engine idle speed. The PCM communicates with the IAC valve by varying the ON time of a
repeating ON/OFF duty cycle. A magnet inside the IAC valve operates a rotary valve that controls the opening of the idle air bypass passage in the
