Abstract: A catalyst 3 which has oxygen storage performance is installed in an engine exhaust passage 2, an oxygen storage amount is estimated based on the output of an upstream air-fuel ratio sensor 4 installed in the upstream of the catalyst 3, and an air-fuel ratio is controlled so that this oxygen storage amount coincides with a target value. When the output of a downstream air-fuel ratio sensor 5 has become lean or rich for longer than a fixed time, the output of the upstream air-fuel ratio sensor 4 is corrected based on the output of the downstream air-fuel ratio sensor 5 placed in the downstream of the catalyst 3. In this way, the output fluctuation due to deterioration of the air-fuel ratio sensor 4 upstream of the catalyst is corrected, and the catalyst oxygen storage amount is always precisely controlled to the target value.

Abstract: An air-fuel ratio controller for an internal combustion engine with a catalytic converter in an exhaust passage has an air-fuel ratio sensor, an engine sensor, and a control unit. The air-fuel ratio sensor produces a signal indicative of an air-fuel ratio of an exhaust gas in the exhaust passage on an upstream side of the catalytic converter. The engine sensor produces a signal indicative of misfiring of the engine. The control unit is operatively coupled to the air-fuel ratio sensor and the engine sensor. The control unit computes an estimated quantity of oxygen to be stored in the catalytic converter based on the signal from the air-fuel ratio sensor, and determines if the engine is misfiring based on the signal from the engine sensor.

Abstract: An oxygen storage amount of the catalyst (3) is estimated using a detection result from a front A/F sensor (4). An HC storage amount is calculated as a time integral of the product of the storage rate by the catalyst (3), the air-fuel ratio and the intake air amount, and a target air-fuel ratio is corrected so that a deficiency relative to a target amount of the oxygen storage amount is compensated based on this computation result.

Abstract: With an electronically controlled throttle type internal combustion engine, where a target opening of a throttle valve is set according to a required output of the engine, and the throttle valve is opened and closed with an actuator so as to obtain a target opening; air quantity learning for learning and correcting the target opening of the throttle valve so as to obtain a target intake air quantity is performed by comparing an intake air quantity estimated based on a detection value of the throttle valve opening and an actually detected intake air quantity, at the time of idling the engine. After completion of the air quantity learning, friction learning for learning and correcting the target opening of the throttle valve so as to obtain a target engine output is performed while feedback controlling the throttle valve opening so that the engine rotation speed approaches a target idle rotation speed, at the time of idling the engine.

Abstract: An air-fuel ratio control system for an automotive internal combustion engine equipped with a fuel injector valve. The control system comprises a sensor for detecting a ratio between air and fuel which form air-fuel mixture in the engine. A controller is provided to control the ratio between air and fuel, and includes a section for calculating the ratio between air and fuel, in accordance with an engine operating condition. A section is provided for calculating a quantity of fuel to be supplied through the fuel injector valve, in accordance with the calculated ratio between air and fuel. A section is provided for calculating a coefficient relating to a feedback control for the ratio between air and fuel, in accordance with the calculated quantity of fuel to be supplied. The feedback control is made in accordance with the ratio between air and fuel detected by the sensor.

Abstract: In an internal combustion engine of gasoline direct injection type, there is arranged a gasoline vapor purging system. The vapor purging system has a vapor purging section which temporarily traps gasoline vapor produced in a fuel supply section of the engine and feeds the gasoline vapor through a vapor purge conduit into an intake section of the engine upon operation of the engine. In the vapor purge conduit, there is installed an electrically actuated valve which controls the flow of the gasoline vapor toward the intake section. The vapor purging system has further a control unit which controls operation of the valve so that a target purging rate of the gasoline vapor toward the intake section is determined based on an amount of gasoline injected to each combustion chamber of the engine through an injector.

Abstract: In a, so-called, lean burn engine having a vaporized fuel processor, a concentration of a vaporized fuel purged into an intake air passage (so-called, a purge concentration) is estimated using a normal type oxygen concentration sensor. Whenever a predetermined interval of time has passed, the engine combustion condition is forcefully and temporarily transferred into a stoichiometric air-fuel mixture ratio combustion condition during which the purge concentration is estimated on the basis of an output signal from the oxygen concentration sensor during an air-fuel mixture ratio feedback control.

Abstract: Acceleration corresponding to individual cylinders can be measured by an apparatus. The apparatus comprises a crankshaft position sensor providing position signals, and a device including a programmed control unit. The device measures a first time period of rotation through a first rotation interval defined by first selected position signals separated by a first angle of rotation. It measures a second time period of rotation through a second rotation interval defined by second selected position signals separated by a second angle of rotation. It also measures a third time period of rotation between the first and second rotation intervals. Each of the first and second rotation intervals includes a selected power stroke. The first instantaneous speed is calculated as a function of the first measured time period and the second instantaneous speed is calculated as a function of the second measured time period.

Abstract: Two catalytic converters are disposed in series midway in an engine exhaust passage, and a by-pass valve selectively introduces exhaust into the upstream converter and a by-pass passage which by-passes the converter. When the catalyst temperature of the upstream catalytic converter exceeds a threshold value A, exhaust is routed to the by-pass passage. The catalyst temperature in the state when exhaust is routed to the upstream catalytic converter under steady state engine running conditions is stored as a convergence temperature depending on the engine running conditions.When exhaust is routed to the by-pass passage, exhaust is re-introduced into the upstream converter only when both the catalyst temperature and the convergence temperature corresponding to the running conditions at that time are less than a threshold value B which is less than the threshold value A.In this way, hunting of the by-pass valve operation is prevented.

Abstract: An engine idle control system for a vehicle causes the engine speed to converge on a target idling speed by feedback control when the engine idles. Whether the engine is revolving by itself or is being driven by the vehicle is detected, and the engine speed is controlled by a proportional feedback control on the basis of the difference between the actual engine speed and the target idling speed when the engine is being driven by the vehicle, and is controlled by a control at least a part of which is an integral feedback control when the engine is revolving by itself.