Unstable Idle
- Check EGR valve for sticking.
- Perform power balance test.
- Check ignition spark.
- Check condition of spark plugs.
- Check fuel pressure. See BASIC TESTING article.
- Check fuel injector operation. See SYSTEM/COMPONENT TESTS article.
- Check Heated Oxygen Sensor (HO2S). See SYSTEM/COMPONENT TESTS article.
- Check for intake air system leak.
- Check compression of engine.
- Inspect ECM harness connector for damaged pins or poor connection.
- Replace ECM with known good unit.