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 in the ENGINE PERFORMANCE Section.
- Check heated oxygen sensor(s). See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
- Check for intake air leak.
- Check idle speed adjuster screw for clogging. See BASIC TESTING article in the ENGINE PERFORMANCE Section.
- Check compression of engine.
- Inspect ECM harness connector for damaged pins or poor connection.
- Replace ECM with known good unit.