2.6L engines utilize a system which consists of the battery, ignition switch, coil, and IC igniter (electronic control unit) built into the distributor, spark plugs and inter-component wiring. Primary current is switched by the IC igniter in response to timing signals produced by a magnetic pickup.
Models using the 2.2L and 2.5L engines are equipped with the "Electronic Fuel Control System''. This consists of a Spark Control Computer, various engine sensors, and a specially calibrated carburetor with an electronically controlled fuel metering system. On fuel injected engines, the computer controls the total amount of fuel injected by slightly modifying the pulses that operate the injectors. The function of this system is to provide a way for the engine to burn a correct air-fuel mixture.
On The Spark Control Computer (also known as the Power Module-this component develops into what is known as the Powertrain Control Module, Single Board Engine Controller or the Single Module Engine Controller on newer vehicles) is the heart of the entire system. It has the capability of igniting the fuel mixture according to different models of engine operation by delivering an infinite number of different variable advance curves. The computer consists of one electronic printed circuit board, which simultaneously received signals from all the sensors and within milliseconds, analyzes them to determine how the engine is operating and then advances or retards the timing.
The distributor, on all three engines, is equipped with both centrifugal and vacuum advance mechanisms on 1981-83 models. The centrifugal advance is located below the rotor assembly, and has governor weights that move in and out with changes in engine speed. As speed increases the weights move outward and cause the reluctor to rotate ahead of the distributor shaft, this advances ignition timing. The vacuum advance has a spring loaded diaphragm connected to the breaker assembly. The diaphragm is actuated by intake manifold vacuum. As the vacuum increases, the diaphragm causes the movable breaker assembly to pivot in a direction opposite to distributor rotation, advancing the ignition timing.
On 1984-87 models, the vacuum advance mechanism has been replaced by a vacuum transducer, located on top of the computer. This unit responds to engine vacuum the way the vacuum advance unit does, but produces an electronic signal that is fed to the computer, instead of acting to advance the ignition timing directly. This allows the computer to tailor the advance curve (the amount of advance the distributor provides) to the operating conditions.