Abstract: An air-fuel ratio controller for an internal combustion engine, which controller is capable of: properly correcting an air-fuel ratio after a start-up explosion; preventing inconveniences such as occurrence of an engine stall, a decrease in an engine rotational speed, and a discharge of exhaust gases containing harmful components; and, allocating an idle time-learning value with reference to a rotational engine speed that is obtained at the time of engine start-up, thereby enhancing convenience of use.

Abstract: An air-fuel ratio control system for an internal combustion includes an air-fuel ratio sensor arranged in the exhaust system, and an ECU which controls an amount of fuel to be supplied to the engine in a feedback manner based on an output from the air-fuel ratio sensor by using an adaptive controller of a recurrence formula type, such that the air-fuel ratio of an air-fuel mixture supplied to the engine becomes equal to a desired air-fuel ratio. Deterioration of a response characteristic of the air-fuel ratio sensor is detected based on at least one adaptive parameter used in the feedback control of the amount of fuel to be supplied to the engine.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter disposed in an exhaust system of the engine, for purifying an exhaust gas emitted from the engine, a first exhaust gas sensor in the exhaust system for detecting an air-fuel ratio of the exhaust gas upstream of the catalytic converter, a second exhaust gas sensor in the exhaust system for detecting the concentration of a component of the exhaust gas which has passed through the catalytic converter, downstream of the catalytic converter, and a correction quantity calculator for determining a correction quantity to correct an air-fuel ratio of the engine based on an output from the second exhaust gas sensor so as to equalize the concentration of the component of the exhaust gas downstream of the catalytic converter to a predetermined appropriate value.

Abstract: Disclosed is an apparatus for controlling the fuel injection quantity for an internal combustion engine. The apparatus includes an operating condition detecting unit for detecting the operating conditions of an internal combustion engine on the basis of the engine speed and the intake air amount or the internal pressure of an intake pipe, a purge control variable calculating unit for calculating the amount of the purge control on the basis of the detected operating conditions, an A/F ratio learning and calculating unit for learning the deviation from the desired A/F ratio control by inputting the effect of the disturbance due to the canister purge and performing the A/F ratio feedback control, a memory unit for storing the deviation learned by the calculating unit, and a fuel injection quantity calculation means unit for determining the fuel injection quantity by the amount of correction based on the result of the learned deviation and the A/F ratio deviation obtained by the A/F ratio control.

Abstract: An air-fuel ratio control system for an internal combustion has a plurality of cylinders and an exhaust system. The air-fuel ratio of exhaust gases emitted from the cylinders is detected by an air-fuel ratio sensor arranged in the exhaust system. The air-fuel ratio of a mixture supplied to each of the cylinders is estimated based on an output from the air-fuel ratio sensor by using an observer for observing an internal operative state of the exhaust system by means of a model representative of a behavior of the exhaust system. Feedback control of an amount of fuel to be supplied to the each of the cylinders is carried out in response to the output from the air-fuel ratio sensor by using a controller of a recurrence formula type, such that the air-fuel ratio of the mixture supplied to the each of the cylinders is converged to a desired value.

Abstract: The present invention provides a method for determining ethanol thresholds for a flexible fuel control system for a motor vehicle capable of operating on more than one type of fuel. Preferably, the ethanol threshold is determined from an off-idle purge-free cell from a matrix of fuel adaptive memory cells normally used to compensate for car-to-car variations in required fueling. The ethanol threshold is periodically reduced to compensate for levels of alcohol creep indicated by the amount of purge-free adaptive memory elevation. If the learned value of percent alcohol content of the fuel is less than the ethanol threshold, gasoline operating parameters are implemented for the internal combustion engine. The off-idle purge-free cell also provides a basis for interpolating an on-board diagnostic (OBDII) ethanol threshold. As such, the OBDII monitors are only enabled if the learned value of percent alcohol content of the fuel is less than the OBDII ethanol threshold.

Abstract: The invention provides a process and apparatus for controlling combustion in an Otto combustion engine in which the control variables that control combustion are determined for a particular power cycle as a function of the detected combustion course of a preceding power cycle. According to the invention, a desired burn-through function value for a particular power cycle is precalculated based on values of pertaining influence factors detected in a preceding power cycle, to determine an actual burn-through function value of the particular power cycle in real time. The desired burn-through function is compared with the actual burn-through function and actualized values for the burn-through function influence factors are determined. These factors are used to determine the control variable values for a subsequent power cycle.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter disposed in an exhaust system of the engine, for purifying an exhaust gas emitted from the engine, a first exhaust gas sensor disposed in the exhaust system for detecting an air-fuel ratio of the exhaust gas upstream of the catalytic converter, a second exhaust gas sensor disposed in the exhaust system for detecting the concentration of a component of the exhaust gas which has passed through the catalytic converter, downstream of the catalytic converter, and a control unit for controlling an air-fuel ratio of the engine based on outputs from the first exhaust gas sensor and the second exhaust gas sensor.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter, a first exhaust gas sensor, and a second exhaust gas sensor. A sliding mode controller determines a correction quantity to equalize the concentration of the component downstream of the catalytic converter to a predetermined appropriate value based on the output from the second exhaust gas sensor. A feedback controller determines a correction quantity to converge the concentration of the component downstream of the catalytic converter toward the predetermined appropriate value, and feed-back controls the rate at which fuel is supplied to the engine with the determined correction quantity.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter in an exhaust system of the engine, for purifying an exhaust gas emitted from the engine, a first exhaust gas sensor in the exhaust system for detecting an air-fuel ratio of the exhaust gas upstream of the catalytic converter, and a second exhaust gas sensor in the exhaust system for detecting the concentration of a component of the exhaust gas which has passed through the catalytic converter, downstream of the catalytic converter. A sliding mode controller determines a correction quantity at a first period to correct the air-fuel ratio of the engine so as to equalize the concentration of the component downstream of the catalytic converter to a predetermined appropriate value, according to a sliding mode control process based on the output from the second exhaust gas sensor.

Abstract: A method and system for adaptive transient fuel compensation in a cylinder of a multi-cylinder engine estimates fuel puddle dynamics for the cylinder by determining parameters of a wall-wetting model every engine cycle of the multi-cylinder engine. Fuel delivery to the cylinder is adjusted dependent on the estimated fuel puddle dynamics.

Abstract: An air-fuel ratio control system for an internal combustion engine has a sensor which detects the air-fuel ratio of exhaust gases in an exhaust passage of the engine emitted from a plurality of cylinders. An air-fuel ratio of a mixture supplied to each of a plurality of cylinders is estimated, based on the detected air-fuel ratio and a model representative of a behavior of the exhaust passage. A cylinder-by-cylinder air-fuel ratio control amount is calculated for use in controlling the air-fuel ratio of the mixture supplied to the each of the cylinders in a feedback manner responsive to the estimated air-fuel ratio of the mixture such that the estimated air-fuel ratio of the mixture supplied to the each of the cylinders is converged to a desired air-fuel ratio. A learned value of the cylinder-by-cylinder air-fuel ratio control amount is calculated.

Abstract: A feedback control system and method for operating an internal combustion engine to provide the desired air/fuel ratio under all running conditions. The feedback control operates when the engine is operating at a mid-range rotational velocity and throttle position and when the air/fuel ratio is between about 15 and 16 to 1 to modify the fuel/air ratio from that achieved by a basic setting that is derived from parameters of engine performance so as to maintain the desired ratio. The basic setting is updated based upon previous feedback control corrections in order to minimize the amount of corrections required and reduce hunting.

Abstract: A fuel management system for a gaseous fuel internal combustion engine is disclosed in which a mass air flow sensor as well as a mass gas flow sensor provide input signals to an electronic control unit (ECU) which then determines the air/fuel ratio. The ECU in turn generates output signals to a fuel valve to control the mass of fuel flow to the engine and thus the air/fuel ratio. A turbocharger bypass valve, a precooler for the gaseous fuel supply, a pressure accumulator upstream from the fuel valve, as well as a system to calibrate the engine to the specific gaseous fuel is described to enhance the accuracy of the fuel management system. An improved pressure balanced valve for controlling the fuel flow to the engine is also provided as well as a cylinder pressure transducer to optionally provide an output signal to the ECU to determine the air/fuel ratio.

Abstract: An air-fuel ratio control system for an internal combustion engine has a first air-fuel ratio sensor arranged in an exhaust passage at a location upstream of a catalyst and a second air-fuel ratio sensor arranged in the exhaust passage at a location downstream of the catalyst. In response to an output from the first air-fuel ratio sensor, an air-fuel ratio correction coefficient is calculated for correcting an amount of fuel supplied to the engine in a manner such that an air-fuel ratio of a mixture supplied to the engine is converged to a desired air-fuel ratio. In response to an output from the second air-fuel ratio sensor, a desired air-fuel ratio correction amount is calculated for correcting the desired air-fuel ratio. A learned value of the desired air-fuel ratio correction amount is calculated, and the desired air-fuel ratio is corrected.

Abstract: An air-fuel ratio control system for an internal combustion includes an air-fuel ratio sensor arranged in the exhaust system, and an ECU which controls an amount of fuel to be supplied to the engine in a feedback manner based on an output from the air-fuel ratio sensor by using an adaptive controller of a recurrence formula type, such that the air-fuel ratio of an air-fuel mixture supplied to the engine becomes equal to a desired air-fuel ratio. Deterioration of a response characteristic of the air-fuel ratio sensor is detected based on at least one adaptive parameter used in the feedback control of the amount of fuel to be supplied to the engine.

Abstract: There is provided an air-fuel ratio control system for an internal combustion engine installed on an automotive vehicle. The control system controls the air-fuel ratio of a mixture supplied to the engine to a value leaner than a stoichiometric air-fuel ratio immediately after the start of the engine. Operating conditions of the engine and/or operating conditions of the automotive vehicle is detected. Starting of the vehicle is predicted based on the detected operating conditions of the engine and/or the detected operating conditions of the automotive vehicle. The air-fuel ratio of the mixture supplied to the engine is changed to a richer value than the leaner value when the starting of the vehicle is predicted.

Abstract: The invention is directed to a method for controlling the composition of the air/fuel mixture for an internal combustion engine. In the method, the mean value of the control oscillation is influenced via a change of the delay times tv with which a sign reversal of the actuating variable change is delayed. The dead time of the control is determined from the time-dependent performance of the control actuating variable and is considered for the change of the delay times tv.

Abstract: An upper limit value of a target purge rate is set as a maximum purge rate PGRMAX, taking stability of air-fuel ratio control into consideration. On this occasion, in addition to time upper-limit purge rate PGTGT, full-opening purge rate PG 100, and limit purge rate PGLMT as maximum purge rates based on an amount of vapor desorbing from the canister, tank vapor purge rate PGTANK is obtained as a maximum purge rate based on an amount of vapor introduced directly from the fuel tank (steps 701 to 704). Then a minimum value is set as the maximum purge rate PGRMAX out of these upper limit values of the respective purge rates (step 705).

Abstract: Fuel vapors are purged from a fuel system into an engine air/fuel intake and the mass flow of such vapors are adaptively learned during a fuel vapor learning mode. When operating in a lean air/fuel operating mode, the lean mode is periodically disabled and the fuel vapor learning mode periodically enabled to update the measurement of inducted fuel vapors. Fuel delivery to the engine is corrected by such measurement to compensate for inducted fuel vapors and maintain engine operation at the desired air/fuel ratio.

Abstract: A method and system for adaptive transient fuel compensation in an engine (300) estimates fuel puddle dynamics for a cylinder in an engine by determining parameters of a wall-wetting model on every engine cycle by measuring a temporal delay (407) between when an identification fuel charge is injected (405) and when a binary-type exhaust gas oxygen sensor (213) switches state. Fuel delivery to the cylinder is adjusted (417) dependent on the estimated fuel puddle dynamics which are a function of the measured temporal delay (407).

Abstract: A feedback control system and method for operating an internal combustion engine to provide the desired air/fuel ratio under all running conditions. The feedback control operates to modify the fuel/air ratio from that achieved by a basic setting that is derived from parameters of engine performance so as to maintain the desired ratio. The basic setting is updated based upon previous feedback control corrections in order to minimize the amount of corrections required and reduce hunting.

Abstract: A fuel metering control system for an internal combustion engine having a plurality of cylinders. The system includes an air/fuel ratio sensor and engine operating condition detecting means for detecting engine operating conditions at least including engine speed and engine load. The basic quantity of fuel injection is determined by retrieving mapped data according to the engine speed and engine load. An adaptive controller is provided to calculate a feedback correction coefficient to correct the quantity of basic fuel injection such that the detected air/fuel ratio is brought to a desired value. The desired air/fuel ratio is corrected by a second air/fuel ratio sensor installed downstream of a catalytic converter.

Abstract: Disclosed is an air-fuel ratio control apparatus, which controls the air-fuel ratio of a flammable air-fuel mixture to be supplied to an engine. This control apparatus controls the air-fuel ratio taking into account that fuel vapor produced in a fuel tank is added to the air-fuel mixture. The fuel vapor produced in the fuel tank is purged into the intake passage of the engine through a canister. An electronic control unit (ECU) controls the amount of fuel to be injected from each injector such that the air-fuel ratio of the air-fuel mixture matches a target air-fuel ratio. At the time the fuel vapor is purged, the ECU learns the density of fuel to be purged based on the detected value of an oxygen sensor. Based on this learned value, the ECU compensates the amount of fuel to be injected from each injector.

Abstract: An air-fuel ratio control system with a high accuracy for an internal combustion engine which is capable of particularly improving the transient response characteristic irrespective of the occurrence of an air-fuel ratio sensor delay and a fuel attachment. An in-cylinder air-fuel ratio is calculated on the basis of engine data obtained in advance so that an neural network (NN) receiving a fuel injection quantity involving the past value and air quantity estimating information such as an intake pressure and outputting a calculated in-cylinder air-fuel ratio undergoes learning.

Abstract: An apparatus for controlling the air-fuel ratio in an internal combustion engine, which quickly responds to a deviation between the actual air-fuel ratio and the target air-fuel ratio in the engine and results in immediate purification of the exhaust gas discharged from the engine.

Abstract: A method and system for fuel delivery to an engine (400) measures when an exhaust gas sensor (413) is in a non-lit-off condition and when the exhaust gas sensor is in a lit-off condition. A control device (409) estimates fuel puddle dynamics for an intake system of the engine when the exhaust gas sensor is in the lit-off condition, and adapts (511) an open-loop fuel parameter table (229) dependent on the estimated fuel puddle dynamics. The control device (409) adjusts fuel delivery to the engine dependent on the fuel puddle dynamics when the exhaust gas sensor is in the lit-off condition, and adjusts fuel delivery to the engine dependent on the open-loop fuel parameter table (229) when the exhaust gas sensor is in the non-lit-off condition.

Abstract: In a method for checking the conversion capability of a catalytic converter, in particular a precatalytic converter associated with internal combustion engines of motor vehicles, the checking is undertaken through the use of a temperature measurement immediately downstream of the catalytic converter. Initially the temperature at the beginning and at the end of a predetermined idling phase is measured for a predetermined number of idling phases, following an overrun phase in predetermined operating states of a motor vehicle with an internal combustion engine. Then the difference of the temperature measurements for each idling phase is formed. The sum of all of the temperature differences and the sum of the duration of the idling phases are formed and subsequently a quotient of these results is formed. This quotient determines an average gradient.

Abstract: A method for controlling processes in a motor vehicle is intended, for example, for open-loop/closed-loop control of combustion processes, transmission switching processes or braking processes. An engine characteristics map is formed by operating quantities of the respective process and is represented by a number of support points. In the corresponding control unit, for each support point a piece of information about the value of the map at the position of the support point is provided. In the open-loop/closed-loop control of the process, for a determined working point of the process at least one map value that is decisive for this working point is determined from the map and taking account of this, at least one control quantity for the emission of a control signal is formed. The map is automatically adapted to a changed process behavior. For the adaptation, a correction value is determined for a certain operating phase of the map.

Abstract: In the present invention, the air-fuel ratio of an engine is controlled by a fist air-fuel ratio control based on the output of an O.sub.2 sensor disposed in an exhaust gas passage downstream of a catalytic converter, and by a second air-fuel ratio control based on the output of an O.sub.2 sensor disposed downstream of the catalytic converter. The first air-fuel ratio control determines the air-fuel ratio correction factor FAF in accordance with the output of the downstream O.sub.2 sensor and a second air-fuel ratio correction factors RSR and RSL. The second air-fuel ratio control determines the values of RSR and RSL in accordance with the output of upstream O.sub.2 sensor. Further, a learning correction of FAF is performed in such a manner that the center value of the fluctuation of FAF agrees with a reference value. When the center value of FAF deviates from the reference value, since the values RSR and RSL fluctuate largely, the fluctuation of FAF also becomes large.

Abstract: A managed fuel air control system is provided that transitions between a closed loop stoichiometric A/F mode and an open loop lean A/F mode of operation. When conditions permit open loop lean operation, the engine A/F is ramped from stoichiometric to the desired lean A/F. Periodically, while operating in the open loop lean mode, the system returns to the closed loop stoichiometric mode to update an open loop correction factor used during the open loop lean mode. The time at stoichiometric is usually limited to the time it takes to correct errors in calibration data that have occurred during open loop operation. During lean operation, the adaptive corrections learned at stoichiometric A/F are applied.

Abstract: A fuel supply control system for an internal combustion engine calculates a basic amount of fuel to be supplied to the engine, based on the rotational speed of the engine and load on the engine. An amount of fuel adhering to the inner wall surface of the intake passage of the engine is estimated to calculate an adherent fuel-dependent correction amount. An amount of fuel carried off from the inner wall surface of the intake passage into at least one combustion chamber of the engine is estimated to calculate a carried-off fuel-dependent correction amount.

Abstract: An apparatus for controlling the air-fuel ratio of an internal combustion engine has an air-fuel ratio sensor for detecting an air-fuel ratio of the internal combustion engine, and a fuel supply control device for controlling an amount of fuel supplied to the internal combustion engine based on the air-fuel ratio detected by the air-fuel ratio sensor. The fuel supply control device has a feedback control system for controlling the amount of fuel supplied to the internal combustion engine through a feedback control loop according to a sliding mode control process in order to equalize the detected air-fuel ratio with a target air-fuel ratio.

Abstract: A fuel injection amount control apparatus for an engine comprises injectors for injecting fuel to an engine and an electronic control unit (ECU) for controlling the injectors. The ECU learns the deviation between the air-fuel ratio of a flammable mixture to be supplied to the engine and the target value. The ECU controls the amount of fuel injection to the engine by reflecting the learning value on the computation of the injection amount. The engine has intake valves, exhaust valves and an apparatus for altering the open/close characteristics of the intake valves. The ECU computes the learning value of the air-fuel ratio in accordance with the behavior of the characteristic altering apparatus and the running conditions of the engine. When the coolant temperature of the engine is low and the learning value is not renewed, the ECU compensates the already updated learning value to a smaller value.

Abstract: Fuel vapor is produced in a fuel tank and absorbed in a canister. The absorbed fuel vapor is purged through a purge passage into an engine induction passage under predetermined engine operating conditions. The air/fuel ratio is learned for air/fuel ratio feedback control. The learning control is inhibited when the fuel temperature exceeds a reference value during the air/fuel ratio feedback control. In another aspect of the invention, a purge valve is provided in the purge passage. The air/fuel ratio correction factor is set at an initial value in response to a movement of a purge valve from its open position toward its closed position.

Abstract: An apparatus for use with an internal combustion engine having a fuel vapor trap from which fuel vapor is purged into the engine through a purge passage having a purge control valve provided therein. The purge control valve is controlled to permit fuel vapor purge through the purge passage based on the existing engine operating conditions. An air/fuel ratio feedback control correction factor is calculated to correct the air/fuel ratio within a predetermined range based on the air/fuel ratio of the mixture supplied to the engine. A gain value is calculated based on a deviation between the air/fuel ratio feedback correction factor calculated with the fuel vapor purge and the air/fuel ratio feedback correction factor calculated without the fuel vapor purge and a purge rate of the fuel vapor flow rate to the intake air flow rate. The calculated gain values are stored in a memory in respective memory locations addressable by different fuel vapor amounts.

Abstract: In a multi-cylinder engine, amounts of fuel injection supplied to respective cylinders are individually corrected on the basis of a signal from A/F sensors in the number less than the number of cylinders of the engine, for example, one A/F sensor, so that the air/fuel ratios for respective cylinders are feedback-controlled at a substantially uniform predetermined air/fuel ratio. Therefore, it is possible to perform precise air/fuel ratio control so as to accurately maintain the air/fuel ratio of the engine at the stoichiometric air/fuel ratio, to reduce the concentrations of HC, CO, and NOx in exhaust gas.

Abstract: An air-fuel ratio control system for an internal combustion engine has an air-fuel ratio sensor arranged in the exhaust system of the engine, for detecting the air-fuel ratio of exhaust gases emitted from the engine, and various engine operating parameter sensors for detecting operating conditions of the engine. An ECU controls the air-fuel ratio of an air-fuel mixture to be supplied to the engine to a desired air-fuel ratio in a feedback manner responsive to an output from the air-fuel ratio sensor. A first learned value for correcting the desired air-fuel ratio is calculated based on the feedback control when the engine is detected to be in a first predetermined operating condition, and a second learned value for correcting the desired air-fuel ratio when the engine is detected to be in a second predetermined engine operating condition. The air-fuel ratio of the air-fuel mixture is controlled to a value leaner than a stoichiometric value, by using the first learned value.

Abstract: An air-fuel ratio control system which calculates a basic injection amount of fuel by state detecting sensors (21) each of which detects an operating state of an internal combustion engine, air-amount detecting sensors (22) each of which detects an intake air amount, an air-fuel ratio sensor (23), and a predetermined data group. Further, the air-fuel ratio control system stores past amount data of injected fuel and air-fuel ratio data at each control cycle. A neuro-computation unit (29) reads values of the data detected by the sensors (21,22) and the stored data to obtain an air-fuel ratio estimate to calculate a correction injection amount of fuel by a neural network of a forward neuro-computing unit (210), which has learned beforehand about relations of the injected fuel amount, the detected air-fuel ratio, parameters, and dead time.

Abstract: The invention relates to a combination of a heated lambda sensor with a stepped or binary sensor characteristic and another heated lambda sensor to determine the lambda value in a gas mixture, e.g. in the exhaust gas preferably of internal combustion engines, the output signal from one lambda sensor being used to calibrate the other one, and the two lambda sensors are arranged closely beside each other, the other lambda sensor having a wide-baud sensor characteristic.

Abstract: Based upon a running condition of an engine, the air-fuel ratio of the fuel mixture supplied to the engine is controlled by open loop control to a target air-fuel ratio. The engine includes a mechanism which adsorbs evaporated fuel from a fuel tank, and a purge conduit which supplies a purge gas which is a mixture of this adsorbed fuel and air to the engine in a predetermined running condition. The purge flow rate is changed according to change in the target air-fuel ratio by controlling the flow rate through the purge conduit according to the proportion between the target air-fuel ratio and a predetermined value. By doing this, deviations in the air-fuel ratio precipitated by purging are eliminated, and the accuracy of air-fuel ratio control is enhanced.

Abstract: A method and system for adaptive transient fuel compensation in a cylinder of a multi-cylinder engine estimates fuel puddle dynamics for the cylinder by determining parameters of a wall-wetting model every engine cycle of the multi-cylinder engine. Fuel delivery to the cylinder is adjusted dependent on the estimated fuel puddle dynamics.

Abstract: An object of the present invention is to carry out air-fuel ratio learning to a high accuracy even in a region such as the idling region wherein the number of acquisitions of air-fuel ratio feedback correction values within a predetermined period is small. Average values A for one fluctuation period of an air-fuel ratio feedback correction coefficient .alpha. are computed and stored in order of computation in a RAM, and an arithmetical mean value B obtained. A weighted average value C of a previous learning correction coefficient .sub.KL and the arithmetical mean value B is then obtained (C=X.multidot.B+(1-X).multidot.K.sub.L). The weighting proportion X is set larger the larger the number of acquisitions of the average value A. C is updated/set as a new learning correction coefficient K.sub.L. In this way, since the updating/setting treatment of the learning correction coefficient K.sub.L is carried out in accordance with the acquisition conditions of .alpha.

Abstract: A system for controlling fuel metering for a multi-cylinder internal combustion engine. In the system, a feedback loop having an adaptive controller and an adaptation mechanism coupled to the adaptive controller for estimating controller parameters .theta. is provided. The adaptive controller calculates a feedback correction coefficient using internal variables including the controller parameters .theta., to correct a quantity of fuel injection obtained by retrieving mapped data by engine speed and engine load, to bring a detected air/fuel ratio to a desired air/fuel ratio. The internal variables of the adaptive controller are set such that the feedback correction coefficient is 1.0 or thereabout, when the engine operation has shifted from an open-loop control region to the feedback control region.

Abstract: A fuel metering control system for an internal combustion engine including a feedback loop having an adaptive controller and an adaptation mechanism that estimates controller parameters .theta.. The adaptive controller corrects the quantity of fuel injection to bring a controlled variable obtained at least based on an output of said air/fuel ratio sensor, to a desired value. The convergence speed of the controller parameters is determined by a gain matrix that has non-diagonal and diagonal element. The system is configured that the controller parameters are determined without calculating the non-diagonal elements of the gain matrix, or without calculating using the non-diagonal elements of the gain matrix in the determination, decreasing calculation volume.

Abstract: Fuel vapor is produced in a fuel tank and absorbed in a canister. The absorbed fuel vapor is purged through a purge passage into an engine induction passage under predetermined engine operating conditions. The air/fuel ratio is learned for air/fuel ratio feedback control. The learning control is inhibited when the fuel temperature exceeds a reference value during the air/fuel ratio feedback control. In another aspect of the invention, a purge valve is provided in the purge passage. The air/fuel ratio correction factor is set at an initial value in response to a movement of a purge valve from its open position toward its closed position.

Abstract: An adaptive closed loop fuel control system generates an index of maturity value which indicates the extent to which parameters which characterize an individual engine have been learned and stored for future use in a non-volatile memory. A timer produces the index of maturity value by measuring the elapsed time during which the fuel control system has successfully operated the engine at or near stoichiometry within a predetermined range of engine speed and load conditions. A backup mechanism counts the number of HEGO sensor state changes as the closed loop controller operates in an adaptive mode, setting the index of maturity to a predetermined value even when the measured adaptation time fails to indicate an adequate amount of adaptive operation.

Abstract: An air-fuel ratio control system for an internal combustion engine includes a LAF sensor and an O2 sensor arranged in an exhaust pipe at respective locations upstream and downstream of a catalytic converter. A desired air-fuel ratio coefficient used in calculating an amount of fuel supplied to the engine is calculated based on operating conditions of the engine, and corrected based on output from the O2 sensor. The air-fuel ratio of a mixture supplied to the engine is feedback-controlled to a stoichiometric air-fuel ratio based on the corrected desired air-fuel ratio coefficient. When the output from the O2 sensor falls within a predetermined range, the desired air-fuel ratio coefficient is not corrected, but held at an immediately preceding value thereof.

Abstract: The operation of a catalyst can be monitored using a two part test. An engine management system is arranged to perturb the oxygen concentration of the exhaust gas of an internal combustion engine such that an oxygen concentration of the gas entering the catalyst varies between oxygen rich and oxygen deficient. A first test involves counting the number of transitions of the gas leaving the catalyst between two predetermined oxygen concentrations in response to a predetermined number of transitions of the gas entering the catalyst. A second test is performed if the first test indicates the catalyst to be faulty. The second test involves forming an integral of the oxygen concentration of the gas leaving the catalyst and correcting the integral for gas flow through the catalyst.

Abstract: In a device having air-fuel ratio sensors upstream and downstream of an exhaust gas purifying catalytic converter with learning carried out based on output values from the downstream air-fuel ratio sensor, independent learning is carried out depending on whether the catalytic converter is active or not. The air-fuel ratio is then controlled based on the output value of the first air-fuel ratio sensor, the output value of the second air-fuel ratio sensor and the learned value. As a result leaning accuracy is increased and air-fuel ratio control performance enhanced.