Backfires

Definition: Fuel ignites in intake manifold, or in exhaust system, making a loud popping noise.
- CHECK:
- EGR operation, for being open all the time. See EGR diagnosis.
- Output voltage of ignition coil.
- For crossfire between spark plugs (distributor cap, spark plug wires, and proper routing of plug wires).
- For intermittent condition in primary ignition system.
- Engine timing - See Vehicle Emission Control Information label.
- For erratic spark timing
- Distributor reference.
- For faulty spark plugs and / or plug wires or boots.
- Faulty AIR check valve.
- PERFORM A COMPRESSION CHECK - LOOK FOR:
- Sticking or leaking valves.
- Proper valve timing.
- Broken or worn valve train parts.