Abstract: A method for controlling a vehicle engine includes predicting an engine parameter with a controller that determines measures of various engine parameters, determines a prediction set including at least one predicted value of a measurable engine parameter, determines an estimation set including at least one estimated value of the engine parameter and controls the engine in response to the estimated engine parameter.

Abstract: In order to determine the fuel quantity to be fed into an internal combustion engine during each stroke of the engine, the air mass sucked into each cylinder for combustion during each intake stroke is determined based on an intake-pipe pressure. A current air mass is determined using a measured value for the intake-pipe pressure. Subsequently, during a period in which there is no change in an air intake cross-section for each cylinder, the air mass is determined using a projected intake-pipe pressure, and the fuel quantity to be fed to each cylinder during the current and subsequent intake strokes is determined based on the air mass determinations and a wall film model.

Abstract: The amount of fuel injected in an engine with variable cam timing is more accurately reflective of engine operating conditions by accounting for the phase angle of the camshaft relative to the crankshaft in the calculation of the cylinder air charge. The cam phase angle for the existing engine speed is sensed and used in the calculation of a manifold filling coefficient which modifies the leakage compensated air flow data obtained from a mass air flow meter. A predicted final cylinder air charge is calculated based on the modified air charge from the manifold filling model and the required fuel for a desired air/fuel ratio is based on the calculated cylinder air charge.

Abstract: A mass airflow based control system for an internal combustion engine is provided which is capable of inferring cylinder air charge during non-steady state periods of operation of the engine. The control system infers cylinder air charge from values of rotational engine speed, air mass flow inducted into the engine, inlet air temperature, engine coolant temperature, and barometric pressure. The control system employs the inferred cylinder air charge value for air/fuel ratio control.

Abstract: A method for accurately determining the measure of mass airflow into an internal combustion engine determines measures of various engine parameters and implements the mathematical modeling technique of prediction and estimation.

Abstract: A control system for controlling fueling and/or timing of a fuel injector in an internal combustion engine. Fuel injection is controlled based upon the recent operating history of the engine. In particular, the difference between the instantaneous speed and the average speed over a previous predetermined period are compared and the difference is utilized in determining a control variable which in turn can be used for selecting fueling and/or timing values. The difference between the instantaneous fueling and the average fueling over a predetermined period can also be used in selecting the control variable. The fuel injector fueling and/or timing is determined utilizing fueling and/or timing values from at least two maps, with the control variable determining the proportions of the timing/fueling valves to be utilized in determining commanded timing/fueling.

Abstract: An electronic fuel injection system operable as a bolt on retro fit replacement for a wide variety of carburetors is disclosed. The system includes a throttle body-injector assembly which, by means of an adapter may be bolted directly to stock intake manifolds using the carburetor mounting bolt holes in the manifold. The throttle body passages and injectors are designed to meet the fuel and air delivery requirements of large displacement engines and an electronic control unit which controls the solenoid actuated injectors in a duty cycle operation is provided with externally accessible adjustments by means of which the system may be adjusted to tune the rate of fuel injection to the fuel delivery requirements of engines of displacements much smaller than the largest displacement engine within the systems capability.

Abstract: The invention relates to a process and a device for determining operating characteristics of a cylinder (1) in a combustion engine in which each cylinder is provided with an intake duct (4) for the air/fuel mixture which is equipped with a member (5) for controlling the flow rate of the said mixture and which opens into the cylinder via an inlet port (6), a pressure sensor (11) being connected to the said intake duct between the control member and the port (6); the pressure sensor (11), which is independent of the components to be monitored, is used to detect in continuous fashion the pressure in the intake duct (4) between the control member (5) and the port (6); this pressure is converted in continuous fashion into an analog electrical signal representative of the pressure and of its variations; and this electrical signal is processed (in 12) in such a way as to obtain at least one desired operating characteristic of the cylinder.

Abstract: A control unit for an internal combustion engine that compensates for variations in injection valve flow rate characteristics by detecting an operation status of the engine and then using this status information to calculate a supply air amount or supply fuel amount in accordance with the detected status. Exhaust gas constituents are detected and then used to correct the calculated supply air or supply fuel amount. The control unit compares the exhaust gas constituents with predetermined values and then uses a neural network to control the supply air amount or supply fuel amount to make any deviation between the exhaust gas constituents and the predetermined value approach zero.

Abstract: This invention concerns an apparatus for detecting a cylinder intake air volume based on the output of an air flow meter installed in an intake manifold. The apparatus determines a weighting average coefficient from predetermined calculation equations, and calculates the weighted average of the output of the air flow meter based on this weighting average coefficient so as to detect the actual cylinder air intake volume. Since the weighting average coefficient is determined from calculation equations and not from a map, the detection of the cylinder intake air volume is simple and precise irrespective of the type of engine. When applied to AFR control systems of an engine, it is preferable to correct the weighted average based on a variation rate of the weighted average when the engine is not running under predetermined high load conditions. AFR control can therefore be performed with accurate timing.

Abstract: A defect of prior art methods for controlling an internal combustion engine based on families of characteristics depending on pressure and rpm is that an air mass being taken in is a function of an air temperature in a cylinder and thus of heating in an intake section. This defect is corrected according to the invention by multiplying a basic fuel value taken from a basic family of characteristics by a factor having a denominator containing a correction temperature being determinative for heating-up the intake air in the intake section as a function of its temperature and of an air flow and being taken from a corresponding family of temperature characteristics.

Abstract: In a fuel injected internal combustion engine, the fuel injection is based on computation rather than direct measurement of air intake. To correct for air intake volume changes caused by external factors, a pressure sensor detects the pressure inside the exhaust manifold and, based on this detected value, a correction is made either to the computed value for air intake, directly to the computation of the amount of fuel to be injected, or both. The corrected air intake volume and the corrected fuel injection amount are then used as the basis for ECU control of the time power is applied to the fuel injector.

Abstract: A system for controlling an air/fuel ratio for an internal combustion engine, using an oxygen concentration sensor having a first chamber for introducing therein exhaust gas of the engine and a second chamber for introducing therein reference ambient air to detect oxygen content in the exhaust gas. In order to eliminate exhaust gas pulsation which could affect on detection accuracy, it is firstly determined if engine operation is in a transient state or in a normal state. Then the detected oxygen concentration value in the preceding cycle is added to the product obtained by multiplying the deviation between the values in the preceding and current cycles by a coefficient .alpha.. The coefficient is made different in the transient state and in the normal state. In the normal engine operation state, the coefficient .alpha. is determined from engine speed and load.

Abstract: A fuel control system for an engine has a fuel injector which injects fuel into an intake passage of the engine. An airflow meter detects the amount of intake air of the engine. A controller controls the amount of fuel to be injected from the fuel injection means on the basis of a dulled value by dulling a present value of the output of the airflow meter so that the preceding value of the output of the airflow meter is reflected in the dulled value in a predetermined proportion. The degree of reflection of the preceding value of the output of the airflow meter in the dulled value is reduced when the relation between the value of the output of the airflow meter and the dulled value is inverted.

Abstract: Air/fuel ratio of an internal combustion engine is controlled by predicting the air charge to enter the engine two cylinder events into the future and then determining the amount of fuel to be injected to achieve a desired air/fuel ratio. A first fuel pulse is injected, and if needed, a second fuel pulse is injected to achieve the needed amount of fuel for the desired air/fuel ratio.

Abstract: A fuel control device of an engine which comprises: an intake pipe pressure detecting means; a crank angle signal generating means; a transient state determining means for determining a transient state of an engine; a transient state correction fuel quantity calculating means; an averaging means for averaging the pressure data in a predetermined crank angle signal period; a basic fuel quantity selecting and calculating means for calculating a basic fuel quantity after selecting an output signal of an instantaneous value of the pressure data or an output signal of the averaging means corresponding with an output level of the transient state correction fuel quantity calculating means; a fuel injection quantity determining means for calculating a fuel injection quantity by using the transient state correction fuel quantity and the basic fuel quantity; a fuel quantity measuring means for measuring a fuel quantity for supplying by injection fuel of the fuel injection quantity by the fuel injection quantity determi

Abstract: An engine control system for an internal combustion engine is equipped with dual air-fuel ratio feedback control systems for feedback controlling air-fuel ratios for two groups of injectors. The system includes a common air flow rate sensor, common to both groups, for detecting a common air flow rate introduced into the cylinders and an individual air-fuel ratio sensor for each group of injectors for determining an air-fuel ratio related value for its respective air-fuel ratio feedback control system. A feedback correction value for correction of fuel injection is determined from the air-fuel ratio ralated values for each air-fuel ratio feedback control system. An air flow rate is corrected based on the feedback correction values for correction of fuel injection for the dual air-fuel ratio feedback control systems. Virtual fuel injection rates for the two groups of injectors are then determined from the corrected air flow rate.

Abstract: A fuel injection control apparatus for an internal combustion engine in which the air taken into the intake manifold by a Karman vortex detector. However, the amount of fuel injected is based on a calculated intake volume. The calculated intake volume for a time interval is a weighted sum of the measured volume and the calculated intake volume of the previous period. This overaging amounts for surge storage in the intake manifold and other input paths.

Abstract: A fuel injection system for an internal combustion engine of the type wherein the lengths of fuel injection pulses (t.sub.i) are based on engine load signals (TL) developed from a measurement of intake manifold pressure (p) and wherein compensation is provided for the fuel injection signals during transitions between different dynamic operating conditions. Transition compensation for the inlet manifold pressure values representative of engine load is achieved by modifying the pressure values in dependence upon incremental pressure differences (.DELTA.p). The pressure difference values (.DELTA.p) used for this purpose can themselves be modified by other engine-dependent factors (F.sub.1, F.sub.2) when the measured incremental manifold pressure differences (.DELTA.p) exceed predetermined thresholds.

Abstract: A digital fuel control system for a small internal combustion engine having a pressure sensor for detecting the instantaneous pressure in the air intake manifold of the engine to generate air pressure data. A microprocessor responsive to the air pressure data generates a fuel quantity output signal indicative of the quantity of fuel to be delivered to the engine. A fuel metering apparatus responsive to the fuel quantity output signal generated by the microprocessor meters the fuel being delivered to a fuel delivery mechanism which delivers the fuel into the air intake manifold of the engine. The microprocessor in response to the air pressure data generated by the pressure sensor determines the engine's speed and the average pressure of the air inhaled by the engine. The engine speed data and air pressure data address a look-up table to extract data indicative of the fuel requirements of the engine.

Abstract: A fuel control apparatus for an internal combustion engine comprises, an air intake quantity detector to detect a parameter related to an air intake quantity for the engine, a filter for filtering an output from the air intake quantity detector, a switch for changing the filter coefficient of the filter on the basis of operational conditions of the engine, a controller to control a fuel supply quantity to the engine on the basis of the output of the filter, and a corrector to correct the fuel supply quantity depending on an error between an output from the filter and another output from the same at a predetermined crank angle when the error exceeds a predetermined value, wherein the predetermined value is changed depending on the filter coefficient which is changed by the switch.

Abstract: A method for estimating and correcting bias errors in a vehicle system which implements iterative prediction and estimation to determine a measure of at least one determinable vehicle engine parameter determines if the vehicle engine is in a substantially steady state condition, determines a measure of error between the predicted and measured values of a control parameter while the vehicle is in the steady state condition, estimates a system bias in response to the determined error, and offsets the system bias in subsequent predictions, thereby reducing the error between the predicted and measured values of the control parameter and increasing the accuracy of the estimations of the determinable vehicle parameter.

Abstract: An apparatus to calculate the intake pipe pressure using the degree of throttle opening and the engine speed, to use this intake pipe pressure to calculate a current intake pipe pressure, and to determine a predicted value from this current intake pipe pressure and control fuel injection duration and/or spark timing. Becuase changes in the atmospheric pressure and changes in the air amount flowing through a bypass bypassing the throttle, etc., cause errors in the values predicted for the intake pipe pressure, there are irregularities in the exhaust emission. the atmospheric pressure and the intake pipe pressure, etc., detected by a pressure sensor are used to correct the predicted value, and prevent irregularities and the like in exhaust emissions.

Abstract: A fuel control apparatus for an internal combustion engine comprises an intake air quantity detecting means for detecting an intake air quantity for the engine, a crank angle detecting means for detecting a crank angle of the engine, a sampling means for sampling the intake air quantity every predetermined time, a first calculating manes for calculating the means value of the sampled values every predetermined crank angle, a switching means for changing the crank angle value in accordance with the revolution speed of the engine, and a second calculating means for calculating a fuel injection quantity on the basis of the calculated means value, and a fuel injection means for injecting fuel to the engine at the fuel injection quantity obtained by the calculation.

Abstract: In a method for calculating the quantity of fuel to be supplied to an internal combustion engine during a dynamic transitional mode, the quantity of fuel is calculated from a corrected intake pressure value pkorr and from the speed n. The corrected intake pressure values pkorr derive from a measured intake pressure value pm taking into consideration the ambient pressure, the ambient temperature, and the time delays between the measured intake pressure pm and the intake pressure actually present in the intake pipe during the dynamic transitional mode. The method guarantees an extremely exact metering of the fuel quantity during the dynamic transitional mode.

Abstract: A car control apparatus in which correction characteristics indicating whether or not various control constants are proper or not are calculated through loop control of one of the car's operation parameters, such as the air-fuel ratio, on the basis of the air-fuel ratio correction factors subjected to learning to thereby rationalize the control constants such as the fundamental injection time so as to realize proper fuel injection and proper ignition timing control.

Abstract: A setting system (14) for setting the quantity of fuel delivered to an internal combustion engine has a first setting unit (10.1.1) and a second control unit (10.2.1). The first control unit emits, as a function of signals which are supplied to it from a first sensor arrangement (11.1), a first manipulated variable to the fuel injection pump (12.1). The second setting unit determines, as a function of signals from a second sensor arrangement (11.2), a second manipulated variable, which likewise would be directly suitable for actuating the fuel injection pump, but which is used to calibrate the first setting unit. The setting system thus set up is used whenever a sensor arrangement is used as second sensor arrangement which is slower, but measures more accurately than the first sensor arrangement. Then, the second manipulated variable corresponds more accurately to a value necessary for achieving a desired lambda value than the first manipulated variable.

Abstract: An airflow meter detects an amount of intake air flowing through an intake passage of the engine, and a fuel injector injects fuel in an amount which is determined according to the amount of intake air detected by the airflow meter. A controller calculates moving averages of outputs of the airflow meter, and the ratio of the difference between each output of the airflow meter and the moving average to a value derived from the moving average. The controller causes the fuel injector to increase the amount of fuel to be fed to the engine when the ratio is not smaller than a predetermined reference threshold value.

Abstract: An open-loop/closed-loop control system for adjusting the air/fuel mixture of an internal combustion engine 12 exhibits an oxygen probe (.lambda.-probe) 14 which is exposed to the exhaust gas of the internal combustion engine 12 and which emits an output signal which represents a measure of the air ratio .lambda.. The control system also has a basic memory 10 for storing fuel-metering times which are used for precontrolling the internal combustion engine 12 to a predetermined air ratio .lambda., a desired-value memory 18 for storing desired values of the air ratio and a closed-loop control device 20 which, in depedence on an output signal of the .lambda.-probe 14 measured and on an associated desired value read out of the desired-value memory 18, corrects the particular fuel-metering time read out of the basic memory 10 and the desired-value memory 18 stores the inverse value of the air ratio .lambda..

Abstract: A fuel injection control apparatus for an internal combustion engine includes a fuel injection valve, a throttle valve positioned in an inlet passage, a bypass passage communicating with the inlet passage downstream of the throttle valve, an arrangement for admitting ambient air into the bypass passage, and means for calculating a normally desired amount of fuel to be injected into the inlet passage by the fuel injection valve based on the air pressure in the bypass passage. In order to compensate for differences between the respective air pressures in the bypass passage and the downstream part of the inlet passage, means are provided for calculating an adjusted amount of fuel to be injected which is different from the normally desired amount of fuel.

Abstract: An electronic fuel injection system operable as a bolt on retro fit replacement for a wide variety of carburetors is disclosed. The system includes a throttle body-injector assembly which, by means of an adapter may be bolted directly to stock intake manifolds using the carburetor mounting bolt holes in the manifold. The throttle body passages and injectors are designed to meet the fuel and air delivery requirements of large displacement engines and an electronic control unit which controls the solenoid actuated injectors in a duty cycle operation is provided with externally accessible adjustments by means of which the system may be adjusted to tune the rate of fuel injection to the fuel delivery requirements of engines of displacements much smaller than the largest displacement engine within the systems capability.

Abstract: An apparatus to calculate the intake pipe pressure using the degree of throttle opening and the engine speed, to use this intake pipe pressure to calculate a current intake pipe pressure, and to determine a predicted value from this current intake pipe pressure and control fuel injection duration and/or spark timing. Because changes in the atmospheric pressure and changes in the air amount flowing through a bypass bypassing the throttle, etc., cause errors in the values predicted for the intake pipe pressure, there are irregularities in the exhaust emissions. The atmospheric pressure and the intake pipe pressure, etc., detected by a pressure sensor are used to correct the predicted value, and prevent irregularities and the like in exhaust emissions.

Abstract: A fuel control apparatus for an internal-combustion engine, capable of accurately determining fuel injection quantity according to exhaust gas recirculation rate regardless of bypass air flow rate and the atmospheric pressure.

Abstract: In a fuel supply control method of an automobile engine wherein a plurality of parameters representing an operating condition of the engine are measured, and a fuel supply quantity is determined based on the measured values so as to attain a target air-fuel ratio, an amount of air flowing into each cylinder in an n-th stroke (n is an arbitrary integer) is calculated for prediction by using the measured parameters in a stroke preceding the n-th stroke, and the fuel supply quantity is determined by the predicted value of the amount of air in the n-th stroke and a target value of the air-fuel ratio in the n-th stroke.

Abstract: An internal combustion engine has an intake air flowmeter which includes a first air flow rate computing means for computing the flow rate of intake air from an output of a hot-wire type air flowmeter in accordance with a first flow rate conversion function, a second air flow rate computing means for computing the intake air flow rate from data concerning a given opening degree of the throttle valve and measured engine speed in accordance with a second flow rate conversion function, and a calibration device for calibrating the first conversion function in accordance with the air flow rate computed by the second air flow rate computing means.

Abstract: An electronic fuel injection system for an internal combustion engine comprising an electronic control system having a central processing unit for detecting engine speed, throttle setting regulating air supply to the engine, exhaust gas concentrations, and for controlling fuel injection. The central processing unit also calculates an open basic injection time, corrected by sensors for engine cooling water and air supply temperature and a closed-loop injection time using an exhaust gas sensor.

Abstract: In an internal combustion engine control system, an electronic circuit accepts a non-linear analog signal from a Mass Air Flow (MAF) sensor and converts it to a digital signal by means of a linear or non-linear analog to digital (A/D) converter. The digital signal is then processed by a two-dimensional look-up table which includes corrections for the MAF sensor non-linearity and additional corrections for non-linearity of the A/D converter. This linearized MAF signal is then integrated or averaged to provide air mass per engine event or average mass air flow during an event. This circuit is useful in obtaining better accuracy in fuel management systems that use MAF sensors, particularly if variable valve control is included as part of the control system. The look up table and integrator can be easily implemented in a digital signal processor or microcontroller.

Abstract: A fuel control apparatus for an internal combustion engine which comprises a pressure detecting means for detecting a pressure in a bypass air passage which bypasses a throttle valve in an air intake system for an internal combustion engine, a first estimating means for estimating a value corresponding to the effective cross-sectional area of the bypass air passage, a second estimating means for estimating a pressure in an intake air pipe of the air intake system on the basis of a pressure value detected by the pressure detecting means and an estimated value of effective cross-sectional area obtained by the first estimating means, and an operating means for calculating a fuel injection quantity on the basis of an estimated value of pressure in the intake air pipe which is obtained by the second estimating means.

Abstract: In an air-fuel ratio control apparatus for an internal combustion engine, an air-fuel ratio sensor detects an air-fuel ratio in response to specified components contained in exhaust gas and an electronic control section receives a signal from the air-fuel ratio sensor to calculate an amount of fuel to be injected from a fuel supplying device so that the air-fuel ratio of a gas mixture to be supplied to the engine approaches a target air-fuel ratio. A parameter of a load for the engine and an engine revolution number are each detected, and the electronic control section calculates a correction coefficient on the basis of the parameter of the load and the engine revolution number, whereby the output of the air-fuel ratio sensor is corrected.

Abstract: In a control apparatus for an internal combustion engine for receiving outputs of a crank angle sensor, air flow sensor, etc., calculating control values from these outputs using a microcomputer to actuate actuators; calculated timings at which the respective actuators are deactuated are compared in advance with each other, the control value for the actuator which should be deactuated earliest is stored in an output compare register, and a deactuation signal for the actuator is generated with count matching of two inputs to a comparator of the output compare register. Thus the respective actuators are sequentially controlled.

Abstract: A system for converting a signal from a substantially linear transducer detecting a parameter on a motor vehicle electronic fuel injection system, and so enabling parameter acquisition to varying degrees of accuracy; wherein the transducer is a potentiometer for detecting the setting of the throttle regulating air intake by the engine; and wherein the conversion system itself comprises an electronic circuit featuring at least one amplifier for supplying at least one signal differing in slope as compared to that supplied by the transducer; and a processing unit for enabling parameter acquisition to a degree of accuracy depending on the modified slope of the signal supplied by the aforementioned electronic means.

Abstract: An air-fuel ratio control system for a two-cycle engine is disclosed, which includes a cylinder, a crank case serving also as a pressure chamber, a fuel injection unit including an injector and a pump, an engine speed detecting element for detecting the engine speed, and a throttle opening degree detecting element for detecting the opening degree of a throttle valve.

Abstract: The quantity of air induced in a cylinder of an engine is estimated by using equations based on various coefficients. The coefficients are stored in a memory and derived in accordance with engine operating conditions. The estimated quantity of induced air is corrected so as to approximate quantity of air actually induced in the cylinder. A basic injection pulse width is calculated based on the corrected air quantity. The basic injection pulse width is corrected by a feedback coefficient, thereby producing a fuel injection pulse width signal for operating a fuel injector of the engine.

Abstract: A fuel injection control system derives a correction coefficient for compensating overshooting component in measurement of an engine load indicative parameter, such as an intake air flow rate. The correction coefficient may be variable in such a manner that it increases according to increasing of the engine load. The correction coefficient may be used for correcting either the measured engine load parameter or the fuel injection amount derived taking the measured engine load.

Abstract: A fuel supply control system derives a basic induction volume efficiency on the basis of an intake air pressure and modifies the basic induction volume efficiency with a correction value which is derived on the basis of an engine revolution speed and the intake air pressure. An induction volume efficiency is derived on the basis of modified basic induction volume efficiency, which derived induction volume efficiency is used for deriving a basic fuel supply amount with the intake air pressure. The basic fuel supply amount thus derived is used for controlling fuel supply for the engine. Derivation of the basic induction volume efficiency is performed by an interrupt routine which may be executed in a predetermined timing derived depending upon a time or in synchronism with engine revolution cycle. The correction value may be derived in a background job.

Abstract: An engine control system in which the sensed intake manifold pressure is initially utilized as the atmospheric pressure, before engine rotation, and is thereafter calculated or updated on the basis of the throttle opening and engine revolution values falling within a detection zone for predetermined time.

Abstract: A fuel control system for an internal combustion engine for controlling fuel supply rate on the basis of the output signal of a vortex flowmeter having variable-frequency filter means, capable of accurately measuring intake air flow to control the fuel supply rate accurately avoiding the erroneous measurement of noises generated during the rapid deceleration of the engine in which the throttle valve is shut. The fuel supply system has operating mode detecting means for detecting the operating mode of the engine, and passband fixing means for fixing the passband of the variable-frequency filter means at a predetermined passband when the operating mode detecting means detects that the engine is in a predetermined deceleration mode.

Abstract: An engine control apparatus for controlling fuel injection on the basis of a pressure value relating to the intake pipe pressure of an engine. All variations in the engine load are monitored and a detection signal is output when any variation is equal to or larger than a predetermined value. A timer is operable for a predetermined time in response to such detection signals. Fuel injection is controlled in response to the pressure value during the period when the timer is operative and in response to a value obtained by performing low-pass filter processing of the pressure value during the period when the timer is inoperative.

Abstract: A fuel control apparatus for an engine uses an N-bit low-resolution A/D converter to convert the analog output of an air intake pressure sensor. The N-bit output of the converter is multiplied by a prescribed constant to obtain a signal having at least (N+1) bits. The (N+1) bit signal is subjected to low-pass digital filtering and is used by a controller to calculate the pulse width to be applied to a fuel injector. A high resolution can be obtained using an inexpensive N-bit A/D converter.

Abstract: An output correction method for an exhaust gas ingredient-concentration sensor for internal combustion engines. The sensor has two sensor elements having output characteristics different from each other. The sensor elements each produce an output proportional to the concentration of an ingredient in exhaust gases emitted from the engine. The sensor controls the air-fuel ratio of a mixture supplied to the engine to a desired air-fuel ratio by the use of an output from at least one of the sensor elements. First, it is determined whether or not the difference between the desired air-fuel ratio and an actual air-fuel ratio represented by the output of at least one of the sensor elements is smaller than a predetermined value. Then, an output value of one of the sensor elements is corrrected based on an output value of the other of the sensor elements when it is determined that the difference is smaller than the predetermined value.