General System Description

IGNITION SYSTEM

DESIGN
The Ignition System for the 2.8 V6 is distributorless. Since there are no moving parts, no noise is generated to interfere with the Knock Sensor system. The system is also easier to maintain as no routine adjustments are necessary.

CONSTRUCTION
The Ignition system consists of the following:

^ Engine Control Module (ECM)
^ Camshaft Position Sensor (CMP Sensor)
^ Crankshaft Position Sensor (CKP Sensor)
^ Engine Coolant Temperature Sensor (ECT Sensor)
^ Engine Speed Sensor (RPM Sensor)
^ Knock Sensor I (KS I)
^ Knock Sensor II (KS II)
^ Power Output Stage
^ Three Double-ended Ignition Coils
^ Ignition Cables
^ Ignition Cable Resistor/connectors
^ Spark Plugs

FUNCTION
The Engine Control Module operates each double-ended ignition coil via the power output stage. The power output stage is an electronic switching device used to fire the coils, it is located behind the engine on the engine compartment firewall.

When the ignition coil fires, spark is supplied to two cylinders at the same time. One plug fires during the compression stroke and ignites the fuel mixture and at the same time the other plug fires during the exhaust stroke.

Coil Firing Diagram:

For Example:

When the spark plug for cylinder #1 fires on its compression stroke, the spark plug for cylinder #6 fires during its exhaust stroke.

After 360° of crankshaft revolution, cylinder #6 is in the compression stroke and cylinder #1 is in the exhaust stroke, both spark plugs are fire as before.

The same procedure is followed for cylinders 2-4 and 3-5.

KNOCK CONTROL
Two Knock sensors are used. The use of two knock sensors makes it possible for the system to "hear" better and be more sensitive.

When engine knocking occurs, the ignition timing is retarded until the knocking is eliminated. Since engine knock limit varies from cylinder to cylinder, knock regulation is done cylinder selectively.

Knock control starts when the engine coolant temperature is 104°F (40°C) or above.

The ignition angle of the knocking cylinder is retarded in 3° steps to a maximum of 12° or until the knocking stops.

If the cylinder knock continues, the ECM will switch from premium fuel ignition map to the ignition map for regular fuel. This allows the ignition timing to be retarded up to three additional degrees.