Abstract: A misfire-detecting system detects a misfire occurring in an internal combustion engine. A value of sparking voltage after generation of an ignition command signal indicative of ignition timing is detected and compared with a predetermined voltage value, and it is determines based upon the results of the comparison whether or not a misfire has occurred in the engine. The determination as to occurrence of the misfire is based upon at least one of a time period over which the detected value of the sparking voltage exceeds the predetermined voltage value, and an area of a portion of detected values of the sparking voltage exceeding the predetermined voltage value.

Abstract: A system for controlling ignition timing of a vehicle internal combustion engine, in which a plurality of sets of ignition timing control characteristics are established in response to the octane numbers of different kinds of fuel which may intentionally or unintentionally be used in the vehicle. The system infers the octane number of the fuel being used from the occurrence state of knock and selects the set of control characteristics corresponding to the selected fuel octane number, whereafter it determines the ignition timing based on the selected set of control characteristics. The system overcomes the problem of unnecessarily reduced torque occurring when the set of characteristics for low octane number fuel is misselected when the vehicle is running on high octane number fuel, as may happen particularly at the time of engine cold start, since during warmup the engine is apt to produce mechanical noise resulting in spurious knock detection.

Abstract: A method of controlling fuel supply to an internal combustion engine, wherein a quantity of fuel for supply to the engine is determined by correcting a basic value of the quantity of fuel determined as a function of at least one operating parameter of the engine by correction values dependent upon operating conditions of the engine, and the determined quantity of fuel is supplied to the engine. A value of at least one predetermined operating parameter of the engine is detected. A single voltage creating means is adjusted to set an output voltage therefrom to a desired value. Predetermined one of the correction values has a value thereof set as a function of the output voltage from the voltage creating means and dependent upon the value of the at least one predetermined operating parameter of the engine.

Abstract: A fuel supply control method for internal combustion engines, which is capable of stabilizing the engine rotational speed to a desired idling speed immediately after the rotational speed of the engine at idle suddenly changes due to an external disturbance such as a change in the electrical load on the engine. The fuel quantity to be supplied to the engine is determined in accordance with operating conditions of the engine in the idling condition, and the determined fuel quantity is corrected by a correction value which is determined in response to the difference between a desired idling speed of the rotational speed of the engine and an actual value thereof. When the absolute value of a detected rate of change in the rotational speed of the engine is larger than a predetermined value, the correction value is corrected to thereby correct the determined fuel quantity.