Backfires

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

PRELIMINARY CHECKS
Perform the careful visual / physical checks as described in Diagnostic Notes.

IGNITION SYSTEM
Check:
^ Proper ignition coil output voltage with spark tester J 26792 (ST 125) or equivalent.
^ Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
^ Spark plug wires for crossfire, also inspect spark plug wires, and proper routing of plug wires.


NOTICE:
If an intermittent condition exists in the ignition system, refer to Ignition System.

ENGINE MECHANICAL
Check:
^ Compression Look for sticking or leaking valves.
^ Valve timing.
^ Intake and exhaust manifold passages for casting flash.

FUEL SYSTEM
Check:
^ Perform fuel system diagnosis check, see Chart A-7 in System Diagnosis/Diagnostic Charts/ A Charts/Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures


^ Fuel injectors, Perform injector balance test, see Chart C-2A in System Diagnosis/Diagnostic Charts/C Charts/Chart C-2A Injector Coil/Balance Test Procedure. Chart C-2A Injector Coil Balance Test Procedure