GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Express 🢒 Engine 🢒 Engine Electrical 🢒 Backfire

Checks

Action

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

Preliminary Check

Refer to Symptoms - Engine Controls .

Ignition System Checks
    • Check the ignition system. Refer to Distributor Ignition (DI) System Diagnosis .
    • Check for crossfire between spark plugs, such as the distributor cap, spark plug wires, and proper routing of the plug wires.

Engine Mechanical Checks
    • Check 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--Refer to Engine Compression Test in Engine Mechanical.
    • Check the intake and exhaust system for fresh air entering the exhaust upstream of the catalytic converter or restrictions.

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

Additional Checks

Check the secondary air injection (AIR) system for proper operation, if applicable.