Backfires

Fuel ignites in the intake manifold, or in exhaust system, making a loud popping noise.

POSSIBLE CAUSE ACTION


EGR open all the time, 1. Check EGR system in "Testing
leaking gasket Procedures" in Emissions
2. Check EGR electronic controls in
"Fuel Injection & Computerized Engine Controls"



Air management valves, Check Air Injection system in
Deceleration valve, "Testing Procedures" in Emissions
Check valves malfunctioning