GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 2003 🢒 Aurora 🢒 Engine 🢒 Engine Controls - 4.0L 🢒 Backfire

Inspection/Test

Action

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

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

Sensor/System

Inspect the following systems for proper operation:

    • Exhaust gas recirculation (EGR) system--Refer to Evaporative Emission Control System Description .
    • Positive crankcase ventilation (PCV) system--Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical-4.0L.
    • Knock sensor (KS) system

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

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

Engine Mechanical
    • Inspect the following conditions:
       - Cylinder compression--Refer to Engine Compression Test in Engine Mechanical-4.0L.
       - Sticking or leaking valve
       - Worn camshaft lobes
       - Valve timing
       - Worn rocker arms--Refer to Valve Rocker Arms Cleaning and Inspection in Engine Mechanical-4.0L.
       - Broken valve springs--Refer to Valve Spring Inspection and Measurement in Engine Mechanical-4.0L.
       - Excessive oil in the combustion chamber-leaking valve seals
    • Inspect for incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - pistons, etc.

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