Tracker 2WD L4-1.6L VIN 6 (2000)
Idle Air Control Motor (IAC): Description and Operation
General
Idle Air Control (IAC) Valve
The Idle Air Control (IAC) valve is attached to the throttle body with two bolts. The IAC valve enables the Powertrain Control Module (PCM) to easily
control engine idle speed by precisely metering the engine's air intake at closed throttle. The IAC valve opens and closes the idle air (bypass) passage
according to signals from the PCM. The PCM determines the correct engine idle speed by using input from various sensors and switches in order to
assess engine status and requirements.
Operation
The powertrain control module (PCM) uses the IAC valve in order to control engine idle speed. The IAC valve is a stepper motor design. The IAC
valve opens and closes the idle air (bypass) passage with a plunger. The plunger moves in and out in response to the rotation of the IAC motor. The
idle air passage allows air to enter the engine without passing over the throttle valve.
The PCM commands the plunger of the IAC valve to retract, in order to increase the idle air passage opening. A larger idle air passage opening allows
more air to enter the intake, resulting in an increase in engine speed.
