Ignition System Description

The Electronic Ignition (EI) system on the 3400 LA1 (VIN E) engine uses a coil pack with one ignition coil for each two cylinders in the engine. Mounted under the ignition coils on each system '8 an Ignition Control Module (ICM) that performs ignition coil switching functions and interacts with the Powertrain Control Module (PCM) to optimize ignition system operation. On these engine systems, the spark timing is controlled electronically. The ICM controls the spark timing during engine start-up, and provides a back-up timing system that will allow the engine to run in the event of an open or ground in the ignition Control (IC) circuit. Once the engine starts and is running above an approximate engine speed of 400 RPM, the PCM takes over the spark timing and sends signals to the ICM for ignition coil switching. The electronic ignition systems used on these engines use a waste spark method of spark distribution. Each cylinder is paired with its opposing cylinder In the firing order, so that one cylinder on compression fires simultaneously with the opposing cylinder on exhaust The spark that occurs in the cylinder that Is on the exhaust stroke is referred to as the waste spark.