Backfires

Definition: Fuel ignites inside intake manifold or in exhaust system, making loud popping noise.

PRELIMINARY CHECKS
^ Perform the careful visual/physical checks as described at start of "Symptoms".

ADDITIONAL CHECKS
^ CHECK: EGR gasket for faulty or loose fit.
^ CHECK: EGR operation for being open all the time. Refer to "Exhaust Gas Recirculation (EGR)" CHART C-7.Chart C-7 EGR System Check
^ CHECK: Intake and exhaust manifold for casting flash.

IGNITION SYSTEM
^ CHECK: Proper ignition coil output voltage with spark tester J 26792 or equivalent (ST-125).
^ 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 Ignition Control (IC) system assembly, spark plug wires, and proper routing of plug wires.

NOTICE: If an intermittent condition exists in the ignition system, refer to "Ignition Control (IC) System".

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

FUEL SYSTEM
^ CHECK: Perform fuel system diagnosis check, see CHART A-7.Related Tests, Information and Procedures
^ CHECK: Fuel injectors. Perform fuel injector coil/balance test, refer to CHART C-2A.Chart C-2A Fuel Injector Balance Test