Chart C-2B: Idle Air Control Valve (Trooper 2.8L): Notes

For Idle Air Control (IAC) valve testing, proceed to TESTING IDLE AIR CONTROL (IAC) VALVE (CHART C-2B, TROOPER 2.8L). See Figure .

1. Continue with test, even if engine will not idle. If idle is too low, Scan tester will display 80 or more counts. If idle is high, it will display zero counts. Occasionally, an erratic or unstable idle may occur. Engine speed may vary 200 RPM or more up and down. Disconnect IAC valve. If the condition is unchanged, the IAC is not at fault.
2. When the engine was stopped, the IAC valve plunger retracted (more air) to a fixed park position for increased airflow and idle speed during the next engine start. A Scan tester will display 100 or more counts. When performing this test, immediately note RPM on start-up. On a warm engine, RPM will decrease rapidly.
3. Ensure IAC valve is disconnected before testing. Test light will confirm the ECM signals with a steady or flashing light on all circuits.
4. There is a remote possibility that one of the circuits is shorted to voltage, which would have been indicated by a steady light. Disconnect ECM and turn ignition on. Probe terminals to check for this condition.