Backfires

SYMPTOM DESCRIPTION:

This condition occurs when fuel ignites in intake manifold, or in exhaust system, making a loud popping noise.


POSSIBLE CAUSE ACTION



IGNITION SYSTEM MALFUNCTION - Scope check Ignition System

- Check IGNITION COIL for proper output voltage.

- Check SPARK PLUGS for proper spark duration. Remove spark plugs, check for fuel fouled plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Replace as necessary.

- Check SECONDARY CIRCUIT for abnormal firing Kv, crossfire between spark plugs (distributor cap, spark plug wires), and proper plug wire routing.

- Check IGNITION TIMING for excessive spark advance or retard.



ENGINE MECHANICAL MALFUNCTION - Check COMPRESSION Perform a compression check, and cylinder leakage test, look for sticking or leaking valves.

- Check for VACUUM LEAKS inspect Intake manifold, gasket(s), and hoses.

- Check exhaust system for leaks, restriction, or damage.



EMISSIONS COMPONENT MALFUNCTION - Check EGR valve for binding or sticking in the open position.

- Check EGR Transducer for proper operation.


FUEL SYSTEM MALFUNCTION - Check for lean Air-Fuel mixture, O2 Sensor, perform injector balance test, inspect regulator operation (check vacuum line and return hose), check fuel pressure



EXHAUST SYSTEM - Check exhaust system for leaks or damage