Abstract: A method for detecting a misfire by fluctuation in crankshaft rotation in which the occurrence of a misfire can be detected exactly by eliminating the effect of detection error in detecting the fluctuation in crankshaft rotation, caused by the error in the construction of a crank angle sensor. By succeedingly receiving pulses from the crank angle sensor, a processor detects a time interval taken from the entering into a crankshaft rotation angle region, relating to a cylinder corresponding to both pulses, to the leaving therefrom (S2), calculates the crankshaft angular acceleration D.omega..sub.n by using the correction factor calculated on the basis of the above detected time interval, and the time interval determined by dividing the time taken for one rotation of the crankshaft by the number of cylinders (S3, S4), the latter interval being free from sensor error, and detects the occurrence of a misfire when the calculated value D.omega..sub.n is less than the decision value (S5 through S7).

Abstract: A misfire detecting method is provided for preventing erroneous detection by prohibiting misfire detection when it is judged that an internal combustion engine is operating in a particular operating condition in which load on the engine can suddenly change, wherein a processor for repeatedly executing a misfire detection process immediately ends the present cycle of the misfire detection process when it is judged that the engine has just been started (S3), when it is judged that the igniton key has just been turned off (S4), or when it is judged that the engine is decelerating, that the transmission is performing a shift operation, or that the vehicle is running on a rough road (S5-7), to thereby avoid erroneous detection which is liable to occur during rough-road travel etc.

Abstract: This invention relates to a control system for the quantity of air to be inducted, which is suitable for use in controlling the idling speed of an engine, for example, for an automotive vehicle or the like. It is an object of the present invention to permit a change of the same degree to the quantity of air to be inducted for the compensation of a load without being affected by the temperature of the engine and also to precisely obtain inducted air in a quantity required inherently.

Abstract: A method for determining a failure of an exhaust gas recalculation (EGR) apparatus in which a failure of the EGR apparatus is determined by determining whether a difference between an intake manifold pressure developed when an EGR valve is open and that developed when the EGR valve is closed falls within a specified range, the EGR valve being temporarily opened and closed while failure determination is being implemented. The failure determination is aborted so as to prevent erroneous determination, if a variation of the engine speed exceeds a specified value during the failure determination, or if a variation of the opening degree of an idling speed control (ISC) valve, disposed in a bypass passage installed in an intake passage of an engine in a manner bypassing a throttle valve, exceeds a specified value during the failure determination, or if a fuel control mode changes during the failure determination.

Abstract: A misfire detection method is provided, which method makes it possible to accurately detect the occurrence/absence of misfire by eliminating a detection error in misfire detection. This error is caused by a vibrational increase or decrease of the rotational changing rate of a crankshaft after a misfire state occurs. A processor, which receives pulse outputs from a crank angle sensor, calculates in sequence angular accelerations D.omega..sub.n-2, D.omega..sub.n-1, D.omega..sub.n, and D.omega..sub.n+1 in crank angle areas which correspond to a preceding cylinder, two cylinders checked for misfire, and a succeeding cylinder, respectively. If the values D.omega..sub.n-1 and D.omega..sub.n n significantly decrease in comparison with the values D.omega..sub.n-2 and D.omega..sub.n-1, respectively, then it is tentatively determined that misfire has occurred in both cylinders checked. Then If the value D.omega..sub.n+1 significantly increases compared to the value D.omega..sub.

Abstract: A misfire detection method based on fluctuation in crankshaft rotation, in which a time interval required for the crankshaft to rotate over an angle region associated with a cylinder checked for misfire is detected in response to pulses supplied from a crank angle sensor having vanes. Next, a deviation of the crankshaft angular acceleration D .omega..sub.n, calculated based on the thus detected time interval and corresponding to the cylinder checked for misfire, from the angular acceleration D .omega..sub.n-3, corresponding to a cylinder belonging to the cylinder group to which the cylinder checked for misfire belongs, is compared with a determination value, and an occurrence/absence of misfire is detected in accordance with a result of the comparison.

Abstract: A method and apparatus of detecting faults for a fuel evaporative emission treatment system, in which the fuel evaporative emission which is admitted from a fuel tank and absorbed once by a canister is separated from the canister by purge air and sucked in a suction pipe of an engine. Under the control of an electronic control unit, a vent port of the canister is closed by closing a vent solenoid valve, and a purge control valve installed in a pipe connecting an outlet port of the canister to the suction pipe is opened. Thereby, a negative pressure of suction air is applied to the fuel tank via another pipe connecting the above-mentioned pipe and the inlet port of canister to the fuel tank to reduce the internal pressure of the fuel tank. Then, the reduction of the internal pressure of the fuel tank is completed by closing the control valve. Afterward, the pressure rise generated in the fuel tank from the time when the exhaust is completed is detected on the basis of the output of a pressure sensor.

Abstract: A failure determination method for an O.sub.2 sensor is provided wherein the air-fuel ratio of a mixture is maintained at a value which produces a leaner or richer air-fuel ratio than a stoichiometric ratio by a predetermined value, for a predetermined time after an engine starts operating in an idle region, to thereby make the oxygen concentration of exhaust gas surrounding the O.sub.2 sensor uniform. Subsequently, the air-fuel ratio is forcibly subjected to an oscillatory change with a predetermined amplitude of .+-.10 to 15% of the stoichiometric ratio with respect to the stoichiometric ratio at a predetermined frequency of several Hz, to determine abnormality of the O.sub.2 sensor based on the change of the output voltage of the O.sub.2 sensor.