Backfires

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

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