GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 Backfire

Checks

Action

DEFINITION: Ignition occurs in the intake manifold, or in the exhaust system, making a loud popping noise.

Preliminary
    • Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.

Sensor/System

Check the following systems for proper operation:

    • The exhaust gas recirculation (EGR) system
    • The PCV system
    • The knock sensor (KS) system

Ignition System
    • Check for proper routing of the IC circuits in each ignition module assembly connector.
    • Check the ignition coils for signs of carbon tracking or damage.
    • Check for proper spark plug boot alignment.
    • Check the spark plugs for proper heat range and reach.

Engine Cooling System
    • Check for proper engine coolant level. Refer to Loss of Coolant in Engine Cooling.
    • Check the engine thermostat for proper operation or for the wrong heat range. Refer to Thermostat Diagnosis in Engine Cooling.

Engine Mechanical
    • Check the following conditions:
       - Cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
       - Sticking or leaking valve
       - Worn camshaft lobes
       - Valve timing
       - Worn rocker arms
       - Broken valve springs
       - Excessive oil in the combustion chamber-leaking valve seals
    • Check for incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - pistons, etc.

Additional Checks
    • Inspect the vacuum hoses for splits, kinks, proper routing, proper connection, and fuel loading. Refer to the Emission Control Information label.
    • Check the AIR check valves for proper operation.
    • Check for proper operation of the torque converter clutch. Refer to Torque Converter Diagnosis in Automatic Transaxle.
    • Check the exhaust system for possible leaks and/or restrictions.