Backfire

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

CHECK:
- Ignition Timing. See Emission Control Information Label on car.
- EGR operation for being open all the time.
- Output voltage of ignition coil.
- For crossfire between spark plugs (distributor cap, spark plug wires, and proper routing of plug wires).
- For faulty spark plugs and/or plug wires or boots.
Perform a compression check - look for sticking or leaking valves.
- For proper valve timing.
- Broken or worn valve train parts or burned intake valve(s).