Backfires

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

INSPECTION
^ Compression, Look for sticking or leaking valves.
^ Exhaust Gas Recirculation (EGR) operation for being open all the time. See Chart C-7A.

^ EGR gasket for faulty or loose fit.

^ Output voltage of ignition coils, using a shop oscilloscope or spark tester J 26792 (ST-i 25) or equivalent.

^ Valve timing.
^ Spark plugs, spark plug wires and proper routing of plug wires.