Engine Backfires: Sensor/System

Inspect the following systems for proper operation:

1. Exhaust Gas Recirculation (EGR) system. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4.6L DEVILLE & SEVILLE article.
2. Positive Crankcase Ventilation (PCV) system. See appropriate article in ENGINES.
3. Knock Sensor (KS) system.