Backfire

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

Visual Check:
- Vacuum hoses for splits, kinks and proper connections, as shown on vacuum hose routing diagram label.
- Ignition wires for cracking or hardness, proper connection, at both the distributor cap and spark plugs.
- Chaffed wiring harness by pulleys or metal edges.

Make sure hot air tube is connected to air cleaner.
Check proper operation of TCA.
Note: Cold engine only - check the following for sticking or faulty operation:
- Carburetor choke, including a vacuum break and throttle linkage. Check choke TVS if used.
Check carburetor accelerator pump operation.
Check for proper operation of EGR valve.
Check for restricted exhaust system.
Check operation of AIR control valve.
Check for crossfire between spark plugs, distributor cap, spark plug wires and proper routing of plug wires.
Check for intermittent condition in ignition system.
- Pick-up coil
- Ignition coil primary connections
Perform a compression check - look for sticking or leaking valves.
- Check for proper valve timing.
- Check for worn or broken valve train parts, or burned intake valve(s).