GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 Envoy - 4WD 🢒 Engine 🢒 Engine Controls - 4.2L 🢒 Backfire

Inspections

Action

Definition: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.

Preliminary

Refer to Symptoms - Engine Controls .

Ignition System

Inspect the ignition system.

Engine Mechanical
    • Inspect the engine for the following the items:
       - Engine compression--Refer to Engine Compression Test in Engine Mechanical.
       - Improper valve timing
       - Manifold gaskets
       - Sticking or leaking valves
    • Inspect the intake and exhaust system for fresh air entering the exhaust upstream of the catalytic converter or restrictions. Refer to Symptoms - Engine Exhaust in Engine Exhaust.

Fuel System
    • Inspect the fuel system. Refer to Fuel System Diagnosis .
    • Perform the fuel injector balance test. Refer to Fuel Injector Balance Test with Tech 2 .