Computers and Control Systems: Description and Operation

��Fig. 52b Motronic System Diagram (Typical):

The Motronic system, provides central microprocessor control of ignition system operation and fuel injection. The system uses an Electronic Control Unit (ECU) which monitors engine and vehicle operating conditions through a variety of sensors to determine proper ignition timing and the amount of fuel required for proper engine operation. The ECU monitors crankshaft position, engine speed and temperature, intake air flow volume and temperature, throttle position and vehicle speed, and exhaust gas oxygen content in order to compute proper ignition timing and the amount of fuel required to maintain acceptable engine performance while controlling exhaust emissions.
The ECU controls ignition timing by controlling current switching in the primary ignition circuit, based on signals from the TDC, reference and engine speed transmitters, and the coolant and air temperature sensors. Crankshaft position and the basic ignition timing are established by the transmitters, and the ECU delays or advances primary current switching depending upon engine speed, coolant temperature and intake air temperature. A conventional type ignition coil is used on these models, however, the ignition distributor is integral with the timing cover and serves only to deliver secondary voltage to the spark plugs in the proper firing order.
Electronic fuel injection is controlled by the ECU based upon signals from sensors which monitor engine and vehicle operating conditions and signals from the exhaust gas oxygen sensor. The ECU controls operation of the fuel pump, cold start system and idle speed control module either directly or through relays, and provides the ground circuit to control fuel injector operation.