Section 190 (Engine Control System - 5.3L - Troubleshooting & Diagnosis): Backfire

2006 Buick Terraza CXL, 3.5 L, AWDSECTION Backfire
WARNING: This page is about a different car, the 2006 Chevrolet Monte Carlo and 2006 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Backfire

Inspections Actions
DEFINITION: Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise.
Preliminary Inspections
Fuel System
Sensor/System
Ignition System
  • Inspect for proper ignition voltage output with J 26792  Spark Tester.
  • Remove spark plugs and inspect for the following:
  • An improper spark plug gap will cause a driveability problem. Refer to Spark Plug Inspection . Gap the spark plugs using a wire gage gap tool. Refer to Spark Plug Replacement .
  • Determine the cause of the fouling before replacing the spark plugs. Refer to Spark Plug Inspection for diagnosis.
  • Visually and physically inspect secondary ignition for the following:
    • Ignition wires arcing to ground
    • Ignition coils arcing to ground
  • Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water.
  • Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 - P0308 .
  • Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .
Engine Cooling System
  • Inspect the engine coolant level for being low. Refer to Loss of Coolant .
  • Inspect the engine thermostat for proper operation and for the correct heat range. Refer to Thermostat Diagnosis .
Engine Mechanical
Additional Inspections
  • Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label.
  • Inspect the intake manifold and the exhaust manifold passages for casting flash.
  • Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate an RPM drop when the TCC is commanded ON. Refer to Torque Converter Diagnosis Procedure .
  • Inspect the exhaust system for possible restrictions. Inspect the following:
    • Inspect the exhaust system for damaged or collapsed pipes.
    • Inspect the mufflers for heat distress or possible internal failure.
    • Inspect for possible plugged catalytic converters. Refer to Restricted Exhaust .
  • Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change may indicate that EMI is present. If a problem exists, inspect for high voltage components near the ignition control circuits.
  • Inspect the park/neutral position (PNP) switch operation.
  • Inspect for faulty motor mounts. Refer to Engine Mount Inspection .
  • Inspect the intake manifold and the exhaust manifold passages for casting flash
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.