Mitsubishi Jidosha Kogyo Kabushiki Kaisha

Yasuhisa Yoshida

Toru Hashimoto

Takuya Matsumoto

Koichi Namiki

Mitsuhiro Miyake

Hitoshi Kamura

Hiroyuki Nakajima

Satoshi Kasai

Mitsuhiko Yanagisawa

Hidetsugu Kanao

Toshiro Nomura

Kazutoshi Noma

Method for detecting misfire by fluctuation in crankshaft rotation

A detecting apparatus for a catalytic converter has a pair of O.sub.2 sensors, arranged individually on the up- and downstream sides of the converter, and an electronic control unit for discriminating reduction of the purifying capacity of a three-way catalyst in the converter. This unit discriminates the reduction of the purifying capacity in accordance with the comparison between a decision value and the ratio between the respective frequencies of outputs from the O.sub.2 sensors. In the case where the O.sub.2 sensor on the upstream side is subject to thermal degradation, its decision value is corrected, or the decision itself is interrupted.

Apparatus for detecting reduction of purifying capacity of catalyst for

Fault diagnosis apparatus for a fuel evaporative emission supressing

Misfire detecting method

A fault diagnosis apparatus for detecting a fault in a fuel evaporative emission suppressing system comprises an electronic control unit. When fault diagnosis execution conditions are fulfilled, the electronic control unit stores an average of integral term values for air-fuel ratio feedback control, operating position of an idling speed control valve, and engine speed, and then actuates a purge control valve of the suppressing system so that the valve opens. In a predetermined time period after the actuation of the purge control valve, the integral term average and the like are stored again. If any changes of the integral term average and other values caused by the actuation of the purge control valve are detected, the suppressing system is concluded to be normal. If no changes are detected, on the other hand, the suppressing system is concluded to be faulty.

Fault diagnosis apparatus for a fuel evaporative emission suppressing

An apparatus for determining a failure of an exhaust gas recirculation (EGR) apparatus includes an electronic control unit. When judging the fulfillment of the failure diagnosis executing condition, the electronic control unit stores the intake pressure detected by a pressure sensor, and then introduces part of the exhaust gas from an engine to an intake passage via an EGR passage to start the EGR for failure diagnosis. Thereafter, the intake pressure is detected again. If a significant change in intake pressure does not occur before and after the execution of the EGR for failure diagnosis, it is judged that the EGR apparatus is faulty. If the failure diagnosis executing condition becomes unfulfilled during the execution of failure diagnosis, the EGR for failure diagnosis is stopped, and the failure diagnosis entailing EGR is prohibited from the time when the EGR for failure diagnosis is stopped until a predetermined period of time has elapsed, by which the deterioration in riding quality and drivability of the vehicle is prevented.

Apparatus and method for determining a failure of an EGR apparatus

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. Alternatively, to prevent erroneous determination, an intake manifold pressure difference is corrected in accordance with a variation of the engine speed or a variation of the ISC valve opening degree during the failure determination, or the ISC valve opening degree is fixed during the failure determination.

Method for determining a failure of an EGR apparatus

Misfire detection method based on a change in crankshaft rotation

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. By using the deviation between the angular acceleration values calculated based on the time intervals detected through the use of the same vane, the bad effect of structural errors of the vanes is canceled, to thereby prevent erroneous misfire detection caused by the vane errors.

Misfire detection method based on fluctuation in crankshaft rotation

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. If the degree of pressure rise is high, it is judged that the fuel evaporative emission system has a fault such as poor airtightness.

Method and apparatus of detecting faults for fuels evaporative emission

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.

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Okazaki, Japan

Yasuhisa Yoshida