The 3.4L and 3.8L engines' distributorless ignition system uses a "waste spark'' method of spark distribution. Each cylinder is paired with its opposing cylinder in the firing order, so that one cylinder on the compression stroke fires simultaneously with an opposing cylinder which is on the exhaust stroke. Since the cylinder on the exhaust stroke requires little of the available voltage to fire its plug, most of the voltage is used to fire the cylinder on compression. The process reverses when the cylinders reverse roles.
Components of this system include 3 ignition coils, ignition coil module, crankshaft position sensor assembly, camshaft position sensor assembly, crankshaft reluctor ring, crankshaft balancer assembly with interrupted ring, and the Engine Control Module (ECM) or Powertrain Control Module (PCM). The coil pack consists of three separate, interchangeable, ignition coils. The ignition coil module or Ignition Control Module (ICM) is located above the power steering pump assembly and is connected to the ECM/PCM. The ignition coil module controls the primary circuit to the coils, turning them on and off.
A magnetic crankshaft position sensor assembly is used in this system. The sensor protrudes from the engine block, within approximately 0.050 in. (1.27mm) of the crankshaft reluctor. The reluctor is a special wheel cast onto the crankshaft assembly that has seven machined slots, six of which are equally spaced 60 degrees apart, and the seventh is spaced 10 degrees from one of the other slots. As the reluctor rotates with the crankshaft, the slots change the magnetic field of the crankshaft position sensor assembly, causing an induced voltage pulse. By counting the time between pulses, the ignition control module can recognize the pulse of the seventh slot. Based on this pulse caused by the seventh slot, the ignition control module sends the reference signal to the ECM/PCM to calculate crankshaft position, used to fire coils in correct sequence, and engine speed.
The camshaft position sensor assembly is located on the engine block behind the water pump assembly, near the lower intake manifold assembly. The camshaft position sensor assembly is used for timing the injectors for sequential fuel injection. This sensor is a hall-effect switch.
The signal crankshaft position sensor assembly inserts through the right side of the engine block at mid-engine, near the crankshaft reluctor ring. Notches in the crankshaft reluctor ring trigger the magnetic pickup sensor to provide timing information to the ECM/PCM. This is a hall-effect sensor.
Base ignition timing is preset when the engine is manufactured, and no adjustment is possible. Timing advance and retard are accomplished through the ECM/PCM with ignition control and knock sensor systems.