Backfires

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

Ignition System
- Ignition Timing.
- 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.

Emission System
- EGR operation for being open all the time.

Engine Mechanical
- For proper valve timing.
- Broken or worn valve train parts or burned intake valve(s).