Fails Emission Test
- Ensure engine is at normal operating temperature.
- Check crankcase for fuel contamination.
- Ensure base timing is correct.
- Check for correct PCV valve operation.
- Check EGR system for correct operation.
- Check Mass Airflow (MAF) sensor.
- Ensure air intake system is not restricted.
- Check vapor recovery system operation.
- Check Engine Coolant Temperature (ECT) sensor operation.
- Check Heated Oxygen Sensor (HO2S) output voltage.
- Ensure fuel system pressure is correct.
- Check fuel tank filler tube for tampering of restrictor. If tampering has occurred, check catalytic converter for lead contamination and exhaust system restriction.
- Check for poor quality fuel containing insufficient cleaning additives.
NOTE:
Prolonged use of poor quality fuel can cause injector clogging and carbon build-up on intake system.