Backfires and Afterfires

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

POSSIBLE CAUSE ACTION


EGR open all the time, Check EGR system in "Testing
leaking gasket Procedures" in Emissions



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