Circuit/System Testing

Inspect the air intake system for the following:
- Modified, damaged, or restricted
- Dirty or deteriorating air filter element
- Crankcase ventilation system for correct operation-Refer to Crankcase Ventilation System Inspection/Diagnosis .
- Water intrusion
- Vacuum leak and other un-metered air downstream of the mass air flow (MAF) sensor
- Intake manifold leak
Inspect the exhaust system for the following:
- Water intrusion
- Exhaust leak
- Damaged, restricted, modified or enhanced exhaust system-Refer to Symptoms - Engine Exhaust .
Inspect the engine mechanical for items that could alter the air flow into the combustion chamber. Refer to Symptoms - Engine Mechanical .