Ignition System Operation Description

This ignition system does not use a conventional distributor and coil. It uses a crankshaft position sensor input to the Engine Control Module (ECM). The ECM then determines Electronic Spark Timing (EST) and triggers the direct ignition system ignition coil.

This type of distributorless ignition system uses a "waste spark" method of spark distribution. Each cylinder is paired with the cylinder that is opposite it (1 - 4 or 2 - 3). The spark occurs simultaneously in the cylinder coming up on the compression stroke and in the cylinder coming up on the exhaust stroke. The cylinder on the exhaust stroke requires very little of the available energy to fire the spark plug. The remaining energy is available to the spark plug in the cylinder on the compression stroke.

These systems use the EST signal from the ECM to control the electronic spark timing. The ECM uses the following information:

• Engine load (manifold pressure or vacuum)
• Atmospheric (barometric) pressure
• Engine temperature
• Intake air temperature
• Crankshaft position
• Engine speed (RPM)