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FUEL INJECTION OPERATION INJECTION SYSTEM All engines used in this section have a sequential Multi-Port Electronic Fuel Injection system. The MPI system is The PCM regulates: • Ignition timing • Air/fuel ratio • Emission control devices • Cooling fan • Charging system • Idle speed • Vehicle speed control Various sensors provide the inputs necessary for the PCM to correctly operate these systems. In addition to the The PCM can adapt its programming to meet changing operating conditions. Fuel is injected into the intake port above the intake valve in precise metered amounts through electrically operated The PCM adjusts injector pulse width by opening and closing the ground path to the injector. Engine RPM (speed) MODES OF OPERATION As input signals to the PCM change, the PCM adjusts its response to output devices. For example, the PCM must There are two different areas of operation, OPEN LOOP and CLOSED LOOP. During OPEN LOOP modes the PCM receives input signals and responds according to preset PCM programming. During CLOSED LOOP modes the PCM monitors the inputs from the upstream and downstream heated oxygen For the PCM to enter CLOSED LOOP operation, the following must occur: 1. Engine coolant temperature must be over 35°F (1.6°C). • If the coolant is over 35°F (1.6°C) the PCM will wait 38 seconds. • If the coolant is over 50°F (10°C) the PCM will wait 15 seconds. • If the coolant is over 167°F (75°C) the PCM will wait 3 seconds. 2. For other temperatures the PCM will interpolate the correct waiting time. 3. O2 sensor must read either greater than 0.745 volts or less than 0.29 volt. 4. The multi-port fuel injection systems has the following modes of operation: • Ignition switch ON (Zero RPM) • Engine start-up • Engine warm-up • Cruise PM FUEL INJECTION 14 - 49 |