Backfire

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

- Loose wiring connector or air duct at MAF
Sensor.
- Compression - Look for sucking or leaking valves.
- EGR operation for being open all the time.
See CHART C-7.
- EGR gasket for faulty or loose fit.
- Valve timing.
- Output voltage of ignition coil using a shop ocilliscope or spark tester J-26792 (ST-125) or equivalent.
- Fuel System Chart A-7
- Injector balance Chart C-2A
- Spark plugs for crossfire also inspect (distributor cap, spark plug wires, and proper routing of plug wires).
- Ignition system for intermittent condition. (See Section 6D).
- Engine timing - see Emission Control
Information label.