Rough Or Unstable Idle
- Check IAC valve for malfunction.
- Ensure fuel system pressure is correct.
- Ensure idle speed is correct.
- Check air intake system for restrictions.
- Use stethoscope to verify operational noise coming from fuel injectors.
- Ensure sufficient secondary spark is available in all cylinders.
- Verify vacuum hose routing is correct and that there are no vacuum leaks.
- Ensure fuel system pressure and volume are correct.
- Check for EGR system malfunction.
- Check coolant temperature sensor operation.
- Check intake air temperature sensor operation.
- Verify throttle position sensor has correct adjustment and resistance value.
- Check air conditioner switch operation.
- Check inhibitor switch operation (automatic transmission).
- Check IAC servo drive signal and operation.
- Check airflow sensor voltage output.
- Check barometric pressure sensor voltage output.
- Check crank angle sensor operation.
- Check vehicle speed sensor operation.
- Check TDC sensor or cylinder No. 1 TDC sensor operation.
- Check electrical connections at fuel injectors.