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The engine start-up (crank), engine warm-up, and wide open throttle modes are OPEN LOOP modes. The IGNITION SWITCH ON (ZERO RPM) MODE When the multi-port fuel injection system is acti- vated by the ignition switch, the following actions When the key is in the ON position and the engine is not running (zero rpm), the auto shutdown (ASD) relay ENGINE START-UP MODE This is an OPEN LOOP mode. The following actions occur when the starter motor is engaged. If the PCM receives a distributor signal, it energizes the auto shutdown (ASD) relay and fuel pump relay. The PCM energizes all six injectors until it deter- mines crankshaft position from the distributor pick-up After determining crankshaft position, the PCM be- gins energizing the injectors in sequence. The PCM When the engine idles within 664 RPM of its target RPM, the PCM compares current MAP sensor value Once the ASD and fuel pump relays have been energized, the PCM: • monitors the coolant temperature sensor, distribu- ENGINE WARM-UP MODE This is a OPEN LOOP mode. The following inputs are received by the PCM: • crankshaft position (distributor pick-up) • manifold absolute pressure (MAP) • engine speed (distributor pick-up) • throttle position • A/C switch • battery voltage The PCM adjusts injector pulse width and controls injector synchronization by turning the individual The PCM adjusts engine idle speed by regulating the idle air control motor and ignition timing. CRUISE OR IDLE MODE When the engine is at operating temperature this is a CLOSED LOOP mode. During cruising speed the • crankshaft position (distributor pick-up) • manifold absolute pressure • engine speed (distributor pick-up) • throttle position • exhaust gas oxygen content • A/C control positions • battery voltage The PCM adjusts injector pulse width and controls injector synchronization by turning the individual The PCM adjusts engine idle speed and ignition timing. The PCM controls the air/fuel ratio according ACCELERATION MODE This is a CLOSED LOOP mode. The PCM recog- nizes an abrupt increase in throttle position or MAP DECELERATION MODE This is a CLOSED LOOP mode. During decelera- tion the following inputs are received by the PCM: • crankshaft position (distributor pick-up) • manifold absolute pressure • engine speed (distributor pick-up) • throttle position • exhaust gas oxygen content • A/C control positions • battery voltage 14 - 122 FUEL SYSTEMS Ä |