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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Sonoma Pickup - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Backfire

Backfire

Checks

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

Preliminary Checks
    • Refer to Symptoms .
    • Search for service bulletins.

Fuel System
    • Check for low fuel pressure. Refer to Fuel System Diagnosis .
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Ensure each injector harness is connected to the correct injector/cylinder. Refer to Engine Controls Schematics .

Ignition System
    • Check for proper ignition voltage output with the spark tester J 26792 or equivalent.
    • Check the spark plugs for the following conditions:
       - Check for wet or fuel fouled spark plugs.
       - Check for cracks on the spark plugs.
       - Check for wear.
       - Check for improper spark plug gap.
       - Check for burned electrodes or heavy deposits.
    • If the spark plugs are fuel or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
    • Check the Ignition Control Module (ICM) for proper ground connection.
    • Check the ignition coils for cracks or carbon tracking.
    • Check the spark plug wires for proper resistance and condition.

Engine Mechanical
    • Check engine mechanical:
       - Check compression.
       - Sticking or leaking valves.
       - Worn camshaft lobes.
       - Valve timing.
       - Bent push rods.
       - Worn rocker arms.
       - Broken valve springs.
       - Excessive oil in combustion chamber-Leaking valve seals.
       - Low cylinder compression.
    • For incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    • Refer to Base Engine Misfire Diagnosis in Engine Mechanical for diagnosis procedures.

Additional Checks
    • Check intake and exhaust manifolds for casting flash.
    • Check the exhaust system for possible restriction. Check the following:
       - Inspect exhaust system for damaged or collapsed pipes.
       - Inspect mufflers for heat distress or possible internal failure.
       - For possible plugged three-way catalytic converter. Refer to Restricted Exhaust System Check and Exhaust System Inspection in Engine Exhaust.