2005 Chevrolet Aveo LS, 4D Sedan, StandardFACTORY OEM SERVICE PROCEDURE

Engine Controls - 1.6L (L91) - Troubleshooting & Diagnosis: Troubleshooting: Backfire

Back Fire

Checks Actions
DEFINITION: Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise.
Preliminary Checks
  • Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls .
  • Search for bulletins.
  • Verify that the engine control module (ECM) grounds are clean, tight, and in the correct locations.
Fuel System
Sensor/System
  • Inspect the air intake system and the crankcase for air leaks.
  • Test the crankcase ventilation valve.
  • Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description and DTC P0327 .
Ignition System
  • Test the ignition voltage output with the J 26792  Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis .
  • Inspect for an intermittent ignition system malfunction in the ignition control circuit. Use the Snapshot feature on the scan tool to locate an intermittent failure.
  • Remove the spark plugs and inspect for the following conditions:
  • An improper spark plug gap can cause a driveability concern. Refer to Ignition System Specifications .
  • If the spark plugs are fouled by gas, coolant, or oil, determine the cause before replacing the plugs. Refer to the following procedures:
  • Inspect the spark plug wires for damage.
  • Wet down the secondary ignition system with water from a spray bottle. Wetting down the secondary ignition system may help locate damaged or deteriorated components. Look/listen for arcing or misfiring as the water is applied.
  • Test the crankshaft position (CKP) sensor for the correct resistance. The CKP sensor resistance may be out of range after a hot soak. The resistance should be between 460-620 ohms.
  • Inspect the ignition coil for cracks or carbon tracking.
Engine Cooling System
Engine Mechanical
Additional Checks
  • Inspect the vacuum hoses for splits and kinks. Verify that the connections and routing are as shown on the Vehicle Emission Control Information label. Refer to Emission Hose Routing Diagram .
  • Test the transmission torque converter clutch (TCC). The scan tool should indicate an engine speed drop when the TCC is commanded ON. Refer to Symptoms - Automatic Transmission in Automatic Transmission - Aisin (81-40LE).
  • Inspect the following exhaust system components:
    • The exhaust system for physical damage
    • The exhaust manifold for a collapsed inner wall
    • The mufflers for heat distress or possible internal failure
    • The three-way catalytic converter(s) for restrictions.

      For more information, refer to Symptoms - Engine Exhaust in Engine Exhaust.

  • Electromagnetic interference (EMI) on the reference circuit can cause an engine misfire condition. You can usually detect EMI with a scan tool by monitoring the engine speed parameter. A sudden increase of the engine speed parameter with little change in actual engine speed may indicate that EMI is present. If a problem exists, inspect the high voltage components near the ignition control circuits.
Factory Service Tools

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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.

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