Abstract: A computer determines whether fuel is supplied to the fuel tank while the engine is stopped. When Yes, an injection quantity varying control is performed immediately after the engine is started in which the fuel injection quantity is varied with respect to each cylinder by correcting the fuel injection quantity by use of the air-fuel-ratio learning correction value that is learned in the previous engine operation and a varying correction value which is particular value with respect to each cylinder. The computer determines a combustion condition in each cylinder (for example, a fluctuation in rotational speed in each cylinder), and computes the varying correction value which is appropriate for the supplied fuel. The air-fuel-ratio learning correction value is computed based on the varying correction value.

Abstract: A cylinder identification device has an intake cam sensor and an exhaust cam sensor which output signals indicative of a rotation angle of the camshaft. The levels of the output signals are varied according to the rotation angle of the crankshaft. The cylinder identification is conducted based on an order of combination variation of the output signal levels. The changing positions of the output signal levels of at least one of the intake cam sensor and the exhaust cam sensor are arranged in such a manner to correspond to positions or right before positions in which the fuel can be initially injected at the time of the engine starting. Thus, the cylinder identification device can identify the initial cylinder in a short period, into which the fuel is initially injected at the time of the engine starting, whereby the startability of the engine is enhanced.

Abstract: A vehicle control system has an electronic control unit for controlling an engine based on various operation parameters detected by a throttle sensor, an intake pressure sensor, an accelerator sensor, a vehicle speed sensor and the like. The electronic control unit is programmed to calculate an inclination of a travel road of the vehicle and a travel distance of the vehicle, and then an atmospheric pressure as a function of the inclination and the travel distance. The electronic control unit is further programmed to calculate upper and lower limits based on the inclination and the travel distance thereby to guard the atmospheric pressure from exceeding above and below the upper and lower limits, respectively.

Abstract: A cylinder identification device has an intake cam sensor and an exhaust cam sensor which output signals indicative of a rotation angle of the camshaft. The levels of the output signals are varied according to the rotation angle of the crankshaft. The cylinder identification is conducted based on an order of combination variation of the output signal levels. The changing positions of the output signal levels of at least one of the intake cam sensor and the exhaust cam sensor are arranged in such a manner to correspond to positions or right before positions in which the fuel can be initially injected at the time of the engine starting. Thus, the cylinder identification device can identify the initial cylinder in a short period, into which the fuel is initially injected at the time of the engine starting, whereby the startability of the engine is enhanced.

Abstract: In an air fuel ratio control for engines, a target operation characteristic of engine speed is set based on a coolant temperature when the engine starts cranking. The target engine speed is variable with time after the engine cranking has started and converges to a speed value lower than a normal target idle speed. Immediately after a complete combustion of air-fuel mixture suplied to the engine is detected, an actual engine speed is compared with a target engine speed corresponding to the target operation characteristics, and an air-fuel ratio of the mixture supplied to the engine is controlled based on a comparison result.

Abstract: A pump control means controls a fuel pump so that fuel pressure supplied into the internal combustion engine becomes lower than a predetermined fuel pressure regulated by a fuel pressure regulator when the operating state of the internal combustion engine is within a predetermined operating state. Thus, the fuel pressure has already been controlled low while the engine state is within the predetermined operating state, so that the fuel leak from the injector during an engine stop is suppressed, thereby reducing an exhaust of deleterious gas when the engine starts again. Further, since the fuel pressure is decreased while the engine works, electric power is not wasted for decreasing the fuel pressure.

Abstract: A pump control means controls a fuel pump so that fuel pressure supplied into the internal combustion engine becomes lower than a predetermined fuel pressure regulated by a fuel pressure regulator when the operating state of the internal combustion engine is within a predetermined operating state. Thus, the fuel pressure has already been controlled low while the engine state is within the predetermined operating state, so that the fuel leak from the injector during an engine stop is suppressed, thereby reducing an exhaust of deleterious gas when the engine starts again. Further, since the fuel pressure is decreased while the engine works, electric power is not wasted for decreasing the fuel pressure.

Abstract: In a method and apparatus which compensates a fuel injection amount by a first fuel enrichment coefficient dependent on an engine coolant temperature during engine warm-up period after engine starting, the fuel injection amount is compensated further by a second fuel enrichment coefficient from a time an engine revolution speed falls until a time a predetermined interval lapses. The second fuel enrichment coefficient may be changed by a throttle valve opening condition and/or an engine intake air pressure. The fuel injection amount may be further compensated further by a third fuel enrichment coefficient until a time another predetermined interval shorter than the predetermined interval lapses, when a fall of the engine revolution speed is large.

Abstract: A spark timing control system includes an engine state detecting device for detecting a state of an internal combustion engine. A vehicle vibration detecting device serves to detect a vibration of a vehicle in a longitudinal direction with respect to the vehicle. A target vehicle vibration value calculating device serves to calculate a target vehicle vibration value on the basis of one of results of detections by the engine state detecting device and the vehicle vibration detecting device. A control quantity setting device serves to set a control quantity of a spark timing so as to control the result of detection by the vehicle vibration detecting device at the target vehicle vibration value by use of an optimal feedback gain which is determined according to a dynamic model of the engine.