Ignition System: Description and Operation

Ignition System 94 Metro:

The ignition circuit consists of the battery, distributor, ignition switch, spark plugs, igniter, and primary and secondary wiring.All models are equipped with an electronic spark control (ESC) ignition system which is monitored and controlled by the engine control module (ECM).

The distributor that is used within the ignition system consists of a signal generator (signal rotor and camshaft position sensor) and rotor. On vehicles with standard emissions the ignitor is internal to the ECM circuitry and determines the best time to fire the ignition coil and spark plugs. On vehicles with upgraded emissions the ignitor is mounted below the ignition coil.

All spark timing changes in the distributor are performed electronically by the ECM. The ECM monitors information from various engine sensors, computes desired spark timing, and signals the distributor to change the timing accordingly. No vacuum or mechanical advance mechanisms are used. The ignition system also includes a noise suppressor condenser and noise suppressor filter to eliminate ignition sound. The noise suppressor filter also provides the tachometer with an ignition signal.