Backfires

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

PRELIMINARY INSPECTION
^ Perform the careful "Visual And Physical Checks" in Preliminary Checks. Testing and Inspection

IGNITION SYSTEM
^ CHECK: Proper ignition coil output voltage with J26792 or equivalent.
^ CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
^ CHECK: Spark plug wires for crossfire. Also inspect distributor cap, spark plug wires, and proper routing of plug wires.
^ CHECK: Ignition timing. Refer to Ignition Timing Adjustment. Ignition Timing

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

ADDITIONAL CHECKS
^ CHECK: Intake and exhaust manifold for casting flash.
^ CHECK: EGR operation (If equipped). Refer to Exhaust Gas Recirculation System Check. Testing and Inspection