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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Ignition Timing: Description and Operation

Ignition timing is determined by the powertrain control module in response to engine operating conditions based on stored data tables or maps.Once ignition tuning has been determined, the powertrain control module interrupts the current to the primary circuit of the ignition coil thus triggering the ignition spark which is supplied to the cylinders through the spark plug wires and spark plugs.