Backfire

DEFINITION:

Fuel ignites in intake manifold, or in 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).
- Engine timing. See Emission Control Information label.
- For faulty spark plugs and/or plug wires or boots.
- For proper valve timing.
- Broken or worn valve train parts or burned intake valve(s).