Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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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.