Backfires

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

INSPECTION
1. Inspect the compression, Look for sticking or leaking valves.
2. Inspect the Exhaust Gas Recirculation (EGR) operation for being open all the time. Refer to Diagnostic Charts / Chart C-7.
3. Inspect the EGR gasket for faulty or loose fit.
4. Inspect the output voltage of ignition coils, using a shop oscilloscope or spark tester J 26792 (ST-i 25) or equivalent.
5. Inspect the valve timing.
6. Inspect the spark plugs, plug wires and proper routing of plug wires.