Backfires

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

CHECK:

- Spark plugs.

- Output voltage of ignition coils, using a spark tester J-26793 (ST-125), or equivalent.

- Ignition system.

- Compression, look for valve train problem, valve timing etc.

- Intake manifold gasket leak, TBI gasket to manifold leak.

- A/C VSV not functioning properly.