General Information

During basic operation, the Powertrain Control Module (PCM) determines the ignition timing required by the engine and determines which ignition coil to use.

The Camshaft Position (CMP) sensor is used only for fuel charging. This sensor allows the Sequential Fuel Injection (SFI) system to inject fuel in cylinder firing order; refer to Fuel Delivery and Air Induction.

Refer to Diagrams/Electrical Diagrams for ignition system wiring diagrams.

Ignition Coils
Two ignition coil packs are used for the 2.5 twin-plug engine. The two ignition coil packs are triggered and timed by the powertrain control module. Each coil pack contains two separate ignition coils for a total of four ignition coils. Each ignition coil fires two spark plugs simultaneously, one spark plug on the compression stroke and one on the exhaust stroke. The spark plug fired on the exhaust stroke uses very little of the ignition coil's stored energy. The majority of the energy is used by the spark plug on the compression stroke. Since these two spark plugs are connected in series, the firing voltage of one spark plug will be negative with respect to ground, while the other will be positive with respect to ground.

Spark Plugs
For production and service in 1998, all eight spark plugs are AWSTF32-F.

Dual Plug Inhibit
Dual Plug Inhibit (DPI) is a function of the powertrain control module that is used when the vehicle is being started. During engine cranking, the powertrain control module will only fire the spark plugs on the right-hand side of the engine. When the engine has started, the powertrain control module will start normal twin-plug operation.