The ECM adjusts engine idle speed through the idle air control valve to compensate for engine load, coolant temperature or barometric pressure changes.
The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control valve regulates air flow through the bypass passage.
The ECM controls engine idle speed by adjusting the position of the idle air control valve. The adjustments are based on inputs the ECM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).
When engine RPM is above idle speed, the IAC is used for the following functions:
Target idle is determined by the following inputs:
Removal & Installation
- Disconnect negative cable from battery.
- Remove electrical connector from idle air control valve.
- Remove idle air control valve mounting screw.
- Remove valve from throttle body. Ensure the O-rings is removed with the valve.
- Carefully place idle air control motor into throttle body.
- Install mounting screw. Tighten screw to 62 inch lbs. (7 Nm).
- Connect electrical connector to idle air control motor.
- Connect negative cable to battery.
- Remove the IAC valve.
- Measure the resistance across the IAC valve terminals.
- The resistance should be about 9.7 ohms (+/- 1 ohm).
- If the valve tests outside of this range, replace it.