Ignition Timing: Description and Operation

Fig. 1 Powertrain Control Module (PCM) Location:

IGNITION TIMING

The ignition system is controlled by the Powertrain Control Module (PCM) which is located in the engine compartment (Fig. 1).

NOTE: Base ignition timing by rotation of distributor is not adjustable.

The PCM opens and closes the ignition coil ground circuit to operate the ignition coil. This is done to adjust ignition timing, both initial (base) and advance and for changing engine operating conditions.

The amount of electronic spark advance provided by the PCM is determined by five input factors: engine coolant temperature, engine rpm, intake manifold temperature, manifold absolute pressure and throttle position.