Backfires

BACKFIRE

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



PRELIMINARY CHECKS

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



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: Ignition system. See "Distributor Ignition (DI)".

^ CHECK: For crossfire between spark plugs (distributor cap, spark plug wires, and proper routing of plug wires.)

^ CHECK: Ignition timing. See "Vehicle Emission Control Information" label.



ENGINE MECHANICAL

^ CHECK: Compression. Perform a compression check - look for sticking or leaking valves.

^ CHECK: Valve timing.

^ CHECK: Intake manifold gasket for vacuum leaks.

^ CHECK: EGR operation for being open all the time.

^ CHECK: Intake and exhaust manifolds for casting flash.