Rough Idle/Missing
- Check for vacuum leaks (oil filler cap, oil dipstick, hose connections, PCV hose, PCV valve and EGR system).
- Check idle speed control valve.
- Check air filter.
- Check idle speed and ensure ignition timing is correct.
- Verify secondary ignition system performance.
- Check airflow meter, coolant temperature sensor and air temperature sensor.
- Check engine compression and valve clearance.
- Check variable induction system (if equipped).
- Check cold start injector and cold start injector time switch.
- Ensure fuel system functions properly (pump, lines, filter and pressure regulator).
- Check fuel injectors (low fuel pressure, clogged or leaking injectors).
- Check power to ECU via fusible links, fuses and EFI main relay.
- Check injection signal circuit.
- Check O2 sensor(s).
- Check Electronic Control Unit (ECU).