Electronic Ignition Control

Distributor Ignition (DI) System Input And Output Chart:

CIRCUIT OPERATION
The ignition timing is controlled by the ECM to help maintain the best blend of engine performance and emissions under all operating conditions.

The ECM uses several sensors to calculate the amount of timing based on a map stored in its memory. The ECM varies the timing during:
^ Starting
^ Warm up
^ Idle
^ Hot engine operation
^ Acceleration
^ Low battery voltage
^ Swirl valve operation

Fig. 34 Power Transistor and Ignition Coil:

POWER TRANSISTOR/IGNITION COIL
The power transistor (mounted near the driver's side strut tower) is a voltage amplifier that allows the signal sent from the ECM to activate the primary circuit in the ignition coil. This induces high voltage in the secondary windings of the ignition coil, providing spark to the distributor cap and plugs.