Abstract: A control device for an internal combustion engine can quickly control, regardless of variation of the quantity of evaporative fuel gas adsorbed in a canister of the engine, the air-fuel ratio to a target value by performing air-fuel ratio feedback compensation control so as not to cause the emission performance of the engine to deteriorate. For the first canister purge performed after the engine is started up, a purge valve is driven for a prescribed period at a prescribed purge flow rate. During the period, the quantity of purged fuel is calculated using an air-fuel ratio feedback factor. Based on the fuel quantity thus calculated, an adsorption quantity estimation section estimates the quantity of evaporative fuel gas adsorbed in the canister.

Abstract: A deterioration diagnosis system for an air fuel sensor mounted to an exhaust pipe of an internal combustion engine. The air fuel sensor determines a mixture ratio of air and fuel fed into the internal combustion engine. In the system, an inclination of an output signal of the air-fuel ratio sensor is calculated; variance of the inclination is calculated; deterioration of the air-fuel ratio sensor is determined based on the variance of the inclination.

Abstract: A control device for an internal combustion engine can quickly control, regardless of variation of the quantity of evaporative fuel gas adsorbed in a canister of the engine, the air-fuel ratio to a target value by performing air-fuel ratio feedback compensation control so as not to cause the emission performance of the engine to deteriorate. For the first canister purge performed after the engine is started up, a purge valve is driven for a prescribed period at a prescribed purge flow rate. During the period, the quantity of purged fuel is calculated using an air-fuel ratio feedback factor. Based on the fuel quantity thus calculated, an adsorption quantity estimation section estimates the quantity of evaporative fuel gas adsorbed in the canister.

Abstract: A first fuel injection valve is arranged in an intake port of an internal combustion engine and also a second fuel injection valve capable of exhibiting a spray property having a vaporization characteristic higher than that of the first fuel injection valve is arranged on the intake air flow downstream side of the first fuel injection valve, the fuel injection is performed by the second fuel injection valve at a cranking time, and after a predetermined time has elapsed from completion of the cranking, the share for the first fuel injection is gradually increased to thereby change-over the fuel injection to that by the first fuel injection valve. Further, at a time of the engine acceleration, a main fuel injection amount is injected by the first fuel injection valve and a fuel injection amount equivalent to an increasing amount for acceleration is injected by the second fuel injection, thereby eventually improving the fuel consumption as well as the exhausting performance.

Abstract: A deterioration diagnosis system for an air fuel sensor mounted to an exhaust pipe of an internal combustion engine. The air fuel sensor determines a mixture ratio of air and fuel fed into the internal combustion engine. In the system, an inclination of an output signal of the air-fuel ratio sensor is calculated; variance of the inclination is calculated; deterioration of the air-fuel ratio sensor is determined based on the variance of the inclination.

Abstract: Whether a misfire occurred is judged based on a comparison between diagnosis data that indicates a variation of an engine rotation speed and a threshold based on engine operating conditions. The misfire judgment is canceled based on a result of a comparison between data indicating an average correlation between the diagnosis data and the threshold, and a threshold for cancellation judgment.

Abstract: Whether a misfire occurred is judged based on a comparison between diagnosis data that indicates a variation of an engine rotation speed and a threshold based on engine operating conditions. The threshold is corrected based on data that indicates an average correlation between the diagnosis data and the threshold.

Abstract: In a diagnosing process in which a target air-fuel ratio in an air-fuel ratio feedback control is forcibly changed, and based on a response time of a detection signal from an air-fuel ratio sensor to the change, a response characteristic of the air-fuel ratio sensor is diagnosed. When the diagnosis is finished, an air-fuel ratio feedback control signal is returned stepwise to a value immediately before the starting of diagnosis.

Abstract: In the diagnosing process in which a target air-fuel ratio in an air-fuel ratio feedback control is forcibly changed, and based on a response time of detection signal from an air-fuel ratio sensor to the change, a response characteristic of the air-fuel ratio sensor is diagnosed, when the diagnosis is finished, an air-fuel ratio feedback control signal is returned in stepwise to a value in just before the starting of diagnosis.

Abstract: In a configuration where it is judged whether or not a misfire occurred, based on the comparison between diagnosis data indicating a variation of an engine rotation speed and a threshold based on engine operating conditions, the misfire judgment is canceled based on a result of the comparison between data indicating an average correlation between the diagnosis data and the threshold, and a threshold for cancellation judgment.

Abstract: In a configuration where it is judged whether or not a misfire occurred, based on the comparison between diagnosis data indicating a variation of an engine rotation speed and a threshold based on engine operating conditions, the threshold is corrected based on data indicating an average correlation between the diagnosis data and the threshold.

Abstract: A diagnosis system for a wide-range A/F sensor receives an air-fuel ratio (A/F) of air-fuel mixture supplied to an engine for the A/F sensor. An control unit of the diagnosis system corrects an A/F controlled object of a feedback control on the basis of a detection result of the A/F sensor to adjust the A/F at a target A/F. The control unit diagnoses an abnormality of the A/F sensor from variation of the detection value of the A/F sensor during a time period from the start of the switching of the target A/F. The control unit sets a control gain of an A/F feedback control at a value greater than a normal control gain during the diagnosis.

Abstract: An apparatus for detecting atmospheric pressure in an internal combustion engine includes an open angle detecting portion for detecting an open angle of a throttle valve, and an atmospheric pressure detecting portion updates the atmospheric pressure based on an aspiration pressure when the open angle of the throttle valve is above a threshold S/L and is increasing.

Abstract: A diagnostic system for detecting a freezing condition of an intake pressure sensor for an engine includes a control unit for checking engine operating parameters after a turn-on of an ignition switch to determining whether the engine is a predetermined state permitting a freeze diagnosis, and for performing the freeze diagnosis only when the engine is in the predetermined state. The control unit monitors a decrease of the intake pressure sensed by the intake pressure sensor as the engine speed increases from a start, and judges a freezing condition to exist if the intake pressure does not become sufficiently low even after the engine speed becomes higher than a predetermined speed level.

Abstract: A diagnostic apparatus for supplying an assist air in an internal combustion engine includes: an assist air passage for guiding intake air from upstream of a throttle valve to a fuel injector installed downstream of said throttle valve; an assist air control valve installed in said assist air passage; a sensor for detecting an engine operating parameter; and a control unit. The control unit includes a data storage portion and a data processing portion. The control unit selectively forces the assist air control valve open and closed upon detection of at least one predetermined diagnosis condition. The control unit then calculates and stores a plurality of values corresponding to changes in the engine operating parameter based on signals received from the sensor, and determines an occurrence of an error with assist air supply based on comparisons of said values with a predetermined value.

Abstract: An intake air temperature TC of a cylinder is estimated from an equation of TC=TA+HEXGIN (TA-TA)+273.degree. K on the basis of a cylinder heat-transfer coefficient HEXGIN, an intake air temperature TA and a cooling water temperature TW. An operation of a first correction coefficient KTA is carried out on the basis of an equation KTA=TTC/TC with the use of an intake air temperature TTC estimated under reference environment. Next, an operation of a finally correction coefficient KTAHOS is carried out on the basis of an equation of KTAHOS=KTA.times.[1.0-{(KTA-1.0).times.KCHOS}] with the use of an air density fine adjustment coefficient KCHOS, and then, by taking advantage of the finally correction coefficient KTAHOS, a fuel injection quantity based on an intake air pressure is corrected.

Abstract: A period of from when the starter switch is turned on or from the start of the fuel injection until when the engine rotation speed has reached a predetermined rotation speed, is detected as a parameter representing the starting performance. After the engine rotation speed has reached a predetermined rotation speed, furthermore, the parameter representing a change in the rotation and the parameter representing rising gradient of the rotation-speed are detected. Then, the parameter representing the starting performance, the parameter representing a change in the rotation and the parameter representing a rising gradient of the rotation speed are weighted to detect the fuel property.

Abstract: In an internal combustion engine where in a predetermined driving state, the air-fuel ratio is feedback-controlled based on a detection signal of an air-fuel ratio sensor and in other driving state, the air-fuel ratio is feed-forward-controlled, the presence or absence of a misfire is judged from the detection signal of the air-fuel sensor at the time of the feed forward control, and when the presence of a misfire is judged, a warning is given.