This ignition system is used on the 3.1L engine only.
The Ignition Coil (IC) distributor has an internal magnetic pick-up assembly that contains a permanent magnet, a pole piece with internal teeth and a pick-up coil. When the teeth of the timer core, rotating inside the pole piece, line up with the pole piece, an induced voltage in the pick-up coil signals the electronic module to trigger the coil primary circuit. The primary current decreases and a high voltage is induced in the ignition coil secondary winding. This voltage is directed through the distributor rotor and secondary leads to fire the spark plugs. This system is the only one that has a mechanical adjustment for base timing.
All spark timing changes in the EST distributor are done electronically by the Electronic Control Module (ECM), which monitors information from various engine sensors, computes the desired spark timing and signals the distributor to change the timing accordingly. A back-up spark advance system is incorporated to signal the ignition module n case of (ECM) failure. No vacuum or mechanical advance is used.
See Figure 1