Abstract: Various systems and methods are described for an exhaust gas sensor coupled to an exhaust system of an engine. One example method comprises, during selected engine fueling conditions, alternating between applying different voltages to the sensor; and identifying an amount of alcohol in fuel injected to the engine based on sensor outputs at the different voltages.

Abstract: Methods systems and device for detecting humidity in air through use of an ammonia sensor included in the exhaust of an engine, such as a diesel engine are provided. In one example, a method for an engine having an exhaust with an ammonia sensor includes adjusting an operating parameter in response to ambient humidity, the ambient humidity based on a first ammonia sensor reading at a first exhaust air-fuel-ratio and a second ammonia sensor reading at a second exhaust air-fuel-ratio.

Abstract: A method for controlling combustion in an engine is provided. The method comprises under a first condition, adjusting an EGR amount of a total cylinder charge in response to engine out NOx levels being below a first threshold. In this way, NOx levels may be used as feedback to control combustion stability.

Abstract: To partially supplant the use of fossil fuels in diesel engines, oxygen-containing fuels, such as biodiesels, are proposed as blending agents in diesel fuel. Engine calibration coefficients to control EGR rate, timings and quantities of fuel injection pulses, turbocharger boost, etc, can be determined to compensate for the lower energy content of such oxygenate blends compared to diesel fuels. According to an embodiment of the disclosure, the fuel quantity of each of multiple injection pulses is increased proportionally to compensate for the impact of oxygenates. An adjustment in the fuel injection quantity is performed in response to a new tank of fuel and the adjustment is applied for that tank of fuel. A fuel compensation factor (FCF) can be determined based on the actual amount of fuel injected compared to the expected amount of diesel fuel at the present operating condition.

Abstract: Systems and methods for continuous automatic adjustment of a control set point of an air-fuel ratio controller of a rich burn engine so as to maintain emissions within a desired range. In an embodiment, a NOx sensor is placed in the exhaust outlet from an exhaust catalyst and the NOx exhaust sensor output is continuously monitored while adjusting the control set point between rich and lean in order to minimize the output from the NOx sensor. Corrections may be continuously made to the set point during operation of the engine to compensate for changes in environmental conditions, engine loads, and other factors.

Abstract: Method for diagnosing a NOx readings recorder which acquires a NOx concentration in an exhaust gas tract of an internal combustion engine and comprises two measuring chambers (110, 120), wherein the exhaust gas to be measured is supplied to the first measuring chamber (110) and an oxygen concentration is set by means of a first oxygen ion pump current (IP1), wherein the second measuring chamber (120) is connected to said first measuring chamber (110) and wherein both measuring chambers are disposed in a solid electrolyte, the oxygen content in the second measuring chamber (120) is determined; the oxygen content is additionally determined by a separate device; the two values characterizing the oxygen concentration are compared and a defective sensor is then suggested if the oxygen concentration value determined in the second measuring chamber (120) deviates from the oxygen concentration value determined by the separate sensor device by a predeterminable magnitude.

Abstract: An engine ECU calculates a rotational variation based on a required rotation time when a complete misfire occurs in a cylinder, a required rotation time when complete combustion occurs in the cylinder, and a required rotation time during the current combustion stroke, and integrates the calculated rotational variation. If it is determined that the number of times the rotational variation has been integrated has reached a predetermined number, the engine ECU calculates an amount of learning value deviation from the integrated rotational variation. If the amount of learning value deviation is equal to or greater than a certain amount, the engine ECU corrects a learning value of a sub-feedback control with respect to the air-fuel ratio.

Abstract: A fuel control system for an internal combustion engine includes a fuel starvation detection module and a fuel pump protection module. The fuel starvation detection module detects when a fuel pump is delivering less than a predetermined amount of fuel based on a fuel level in a fuel tank, a fuel pressure in the fuel pump, and an air/fuel (A/F) ratio of the engine. The fuel pump protection module decreases an amount of fuel supplied to the engine during a period after detecting that the fuel pump is delivering less than the predetermined amount of fuel.

Abstract: An engine control system includes a saturation determination module, an adjustment factor generation module, and a fuel control module. The saturation determination module determines when a first exhaust gas oxygen (EGO) sensor is saturated, wherein the first EGO sensor is located upstream from a catalyst. The adjustment factor generation module generates an adjustment factor for an integral gain of a fuel control module when the first EGO sensor is saturated. The fuel control module adjusts a fuel command for an engine based on differences between expected and measured amounts of oxygen in exhaust gas produced by the engine, a proportional gain, the integral gain, and the integral gain adjustment factor.

Abstract: A method of stoichiometrically operating a diesel-fueled internal combustion engine. A control unit is provide with stored data representing, within a range of exhaust valve timing or event modifications, an amount of fresh air flow and exhaust gas residuals resulting from each modification. During operation of the engine, the control unit is used to determining a desired amount of exhaust gas residuals for a given engine load; accessing the stored data to determine a modification that will provide the desired amount of exhaust gas residuals; and generating a control signal that will result in the desired modification.

Abstract: Methods and system for controlling air-fuel ratios in an internal combustion engine are disclosed. One embodiment comprises, adjusting a sensor calibration correction value of an exhaust sensor upstream of a catalyst based on an exhaust sensor downstream of the catalyst. The adjustment of the sensor calibration correction value takes advantage of the fact that certain aromatic hydrocarbons causing errors in the reading of the upstream sensor are not present at the downstream sensor due to sufficient catalytic activity of a catalyst positioned between the sensors.

Abstract: A sensor detection controller is used in combination with a capacitive sensor that is mounted on a seat of a vehicle in such a manner that a capacitance of the capacitive sensor changes according to whether the seat is occupied. The sensor detection controller has a fault detection mode and a normal detection mode. The sensor detection controller includes a signal source for applying an amplitude signal to the capacitive sensor, a switch for switching a signal path, through which the amplitude signal is applied, between the fault detection mode and the normal detection mode, a signal detector for detecting a change in a voltage or a current of the amplitude signal when the amplitude signal is applied, and an impedance member connected to the signal path.

Abstract: Provided is a control apparatus for an internal combustion engine which is capable of estimating a single composition concentration based on an air-fuel ratio correction amount obtained by using an output of an air-fuel ratio sensor in exhaust gas and optimizing a fuel injection amount by using a concentration estimation value. When fueling is performed again during alcohol concentration change after the fueling, an alcohol concentration estimation period or a start determination period for the alcohol concentration change is extended by an integrated fuel injection amount from initial fueling until refueling, whereby alcohol concentration estimation accuracy is improved with respect to the alcohol concentration change due to the initial fueling and the refueling.

Abstract: A Method for estimating NOx creation in a combustion process of a four-stroke internal combustion engine includes monitoring engine sensor inputs, modeling parameters descriptive of said combustion process based upon said engine sensor inputs, and estimating NOx creation with an artificial neural network based upon said parameters.

Abstract: Various systems and methods are described for operating an engine in a vehicle in response to an ambient humidity generated from an exhaust gas sensor. One example method comprises, during engine non-fueling conditions, where at least one intake valve and at least one exhaust valve of the engine are operating, generating an ambient humidity from the exhaust gas sensor and, under selected engine combusting conditions, adjusting an engine operating parameter based on the ambient humidity.

Abstract: A control unit is provided for fuel supply regulation during a cold-running phase of an internal combustion engine, that includes, but is not limited to an input port for inputting a combustion signal about the presence of a rich or lean combustion of a fuel mixture in the internal combustion engine, a P-element for providing a P-manipulated variable, which sets a fuel reduction upon the presence of a rich combustion and sets a fuel increase upon the presence of a lean combustion, an I-element for providing an I-manipulated variable, which sets a fuel increase, and an output port for controlling a fuel supply, the P-manipulated variable and the I-manipulated variable substantially offsetting one another during the cold-running phase upon the presence of a rich combustion in the stationary state.

Abstract: An exhaust gas re-induction apparatus and system. The exhaust gas re-induction apparatus is coupled to an exhaust system or catalytic converter of an engine. The exhaust gas re-induction apparatus includes an oxygen sensor substitute apparatus having an exhaust gas diffusion chamber disposed therein, and an exhaust gas interface housing to receive the oxygen sensor substitute apparatus. A recirculation conduit connects the exhaust gas re-induction apparatus to an air inlet of an engine. The oxygen sensor substitute apparatus includes a coupling section to attach the oxygen sensor substitute apparatus in place of an oxygen sensor apparatus. The oxygen sensor substitute apparatus also includes an exhaust gas dispersion section having a plurality of orifices for dispersing exhaust gas. The exhaust gas re-induction apparatus and the recirculation conduit have always-open passages in which the exhaust gas is recirculated to the engine at different rates depending essentially on the operating speed of the engine.

Abstract: A calibration method comprises: determining a steady-state (SS) delay period from a first mapping of SS delay period indexed by air per cylinder (APC); determining a predicted delay period based on first and second dynamic compensation variables; outputting a theoretical delay period based on a calibration APC; determining the theoretical delay period from a second mapping of theoretical delay period indexed by APC; generating the calibration APC; populating the first mapping based on the theoretical delay and the calibration APC; determining the first and second dynamic compensation variables based on comparisons of the theoretical delay and the SS delay period; and selectively adjusting an amount of fuel provided to the cylinder based on the predicted delay period.

Abstract: A device for generating exhaust gas including a exhaust gas channel and a system. The system includes: a plurality of Bragg gratings distributed in positions transversely to the direction of flow of an exhaust gas at the end of the exhaust gas channel; an optical wave guide structure includes at least one optical wave guide and the Bragg gratings; and a heating device arranged adjacently to the Bragg gratings and through which the Bragg gratings are subjected to heat, or a cooling device arranged adjacently to the Bragg gratings, through which the Bragg gratings can be subjected to cold. The optical wave guide structure and the heating device or the cooling device are arranged at the end of the exhaust gas channel at a distance from an outlet of the exhaust gas into the surroundings of the device.

Abstract: A system includes a cylinder equivalence ratio (EQR) module, a location estimation module, a sensor module, and a fuel control module. The cylinder EQR module determines a first EQR corresponding to a first exhaust gas expelled from a first cylinder and determines a second EQR corresponding to a second exhaust gas expelled from a second cylinder. The location estimation module determines when the first and second exhaust gases mix in an exhaust manifold to form a third exhaust gas having a third EQR. The sensor module estimates an EQR of a fourth exhaust gas based on the third EQR. The fourth exhaust gas is located at an oxygen sensor in the exhaust manifold. The fuel control module controls an amount of fuel supplied to an engine based on a difference between the estimated EQR and an EQR corresponding to measurements from the oxygen sensor.

Abstract: According to a first aspect of the present invention, there is provided an apparatus for detecting variation abnormality in an air-fuel ratio between cylinders comprising a wide-range air-fuel ratio sensor and an O2 sensor provided in an exhaust passage upstream of an exhaust gas purifying apparatus arranged in the exhaust passage for an internal combustion engine having a plurality of cylinders, air-fuel ratio controlling unit for performing air-fuel ratio control for a predetermined period in such a manner as to make an exhaust air-fuel ratio be equal to a stoichiometric air-fuel ratio based upon output from the wide-range air-fuel ratio sensor, and abnormality detecting unit for detecting variation abnormality in an air-fuel ratio between cylinders based upon output from the O2 sensor for the predetermined period when the air-fuel ratio control is performed.

Abstract: A air-fuel ratio control apparatus, applied to an internal combustion engine having a catalyst disposed in an exhaust passage of the engine, includes a downstream air-fuel ratio sensor (oxygen concentration cell type oxygen concentration sensor) disposed at a position downstream of the catalyst, and air-fuel ratio control means for controlling, based on an output value of the downstream air-fuel ratio sensor, an air-fuel ratio of a mixture supplied to the engine so as to change an air-fuel ratio of a catalyst inflow gas. Further, the air-fuel ratio control means controls the air-fuel ratio of the mixture supplied to the engine.

Abstract: A steady-state (SS) delay module determines a SS delay period for SS operating conditions based on an air per cylinder. A dynamic compensation module determines a predicted delay period based on first and second dynamic compensation variables for dynamic operating conditions, the SS delay period, a previous predicted delay period. The first dynamic compensation variable corresponds to a period between a first time when fuel is provided for a cylinder of an engine and a second time when exhaust gas resulting from combustion of the fuel and air is expelled from the cylinder. The SS and predicted delay periods correspond to a period between the first time and a third time when the exhaust gas reaches an exhaust gas oxygen sensor located upstream of a catalyst. A final equivalence ratio module adjusts fuel provided to the cylinder after the third time based on the predicted delay period.

Abstract: A method for operating an internal combustion engine includes monitoring oxygen concentration in an exhaust gas feedstream, a mass flowrate of intake air, and a commanded fuel pulse of fuel. A blend ratio of biodiesel fuel and petrodiesel fuel of the fuel is determined. Engine operation is controlled in response to the blend ratio of biodiesel fuel and petrodiesel fuel of the fuel.

Abstract: An outer housing and method of forming a mounting boss therein, the outer housing comprising: an elongated housing portion defining an inlet opening and an outlet opening, the elongated housing portion having a thickened area defined by an overlapping portion of the elongated housing; a sensor mounting boss formed in the overlapping portion with only displaced portions of the overlapping portion; and a plurality of threads disposed in the sensor mounting boss.

Abstract: A fuel injection amount control system acquires a pre-correction air-fuel ratio imbalance index value that increases as the degree of ununiformity in the air-fuel ratio among cylinders increases, based on an output value of an upstream air-fuel ratio sensor, and obtains a value (intake air amount correlation value) corresponding to the intake air amount and a value (engine speed correlation value) corresponding to the engine speed over a period in which the pre-correction air-fuel ratio imbalance index value is acquired. Also, a post-correction air-fuel ratio imbalance index value is acquired by correcting the pre-correction air-fuel ratio imbalance index value based on the intake air amount correlation value and the engine speed correlation value, and the air-fuel ratio of the engine is controlled based on the post-correction air-fuel ratio imbalance index value.

Abstract: A fuel injection amount control system acquires an air-fuel ratio imbalance index value that increases as the degree of ununiformity in the air-fuel ratio among cylinders increases, based on an output value of an upstream air-fuel ratio sensor, and acquires an imbalance index learned value by performing a first-order lag filtering operation for removing noise, on the air-fuel ratio imbalance index value. Also, the fuel injection amount is increased based on the imbalance index learned value. In the filtering operation, the time constant of the filter is set to a smaller value when a magnitude of a difference between the current value and the last value of the air-fuel ratio imbalance index value is equal to or larger than a threshold value.

Abstract: The invention concerns a procedure and a device for an adaptation of a dynamic model of an exhaust gas probe, which is a component of an exhaust pipe of a combustion engine and with which a lambda value is determined for regulating an air-fuel composition, whereby a simulated lambda value is calculated parallel to that in a control unit or in a diagnosing unit of the combustion engine and an application function uses the simulated and the measured lambda value. According to the invention it is thereby provided that a jump behavior of the exhaust gas probe is determined during a running vehicle operation by evaluating a signal change at a stimulation of the system and that the dynamic model of the exhaust gas probe is adapted with the aid of these results.

Abstract: An internal combustion engine control device and a control method therefore in which feedback control is performed such that a detected air-fuel ratio of exhaust gas detected on the basis of a critical electric current flowing in a solid electrolyte layer of an air-fuel ratio sensor when an air-fuel ratio detection voltage is applied between an exhaust-side electrode layer and an atmosphere-side electrode layer of the sensor matches a stoichiometric air-fuel ratio. When a parameter acquired as an imbalance determination parameter is larger than an imbalance determination threshold, an air-fuel ratio inter-cylinder imbalance state is determined to have occurred.

Abstract: The fact that “with respect to a process in which the output value of a downstream air-fuel ratio sensor (sensor output value) is inverted from the minimum output value to the maximum output value during execution of an active control, the local maximum and minimum values of the secondary differential value of the sensor output value is widely affected by the size of the response delay of the downstream air-fuel ratio sensor and the size of the degree of the degradation of the three-way catalyst” is utilized. By preliminarily acquiring and memorizing, as maps, these relations obtained through an experiment, and applying the “local maximum and minimum values of the secondary differential value of the sensor output value” calculated from the transition of the sensor output value acquired during execution of the active control to the maps, the response delay (time constant) of the downstream air-fuel ratio sensor is acquired.

Abstract: A diesel fuel composition is disclosed, as well as a method for reducing NOx and smoke emissions from a diesel engine at minimum fuel consumption which comprises adding to the diesel engine at least one diesel fuel or blending component for a diesel fuel which has a combination of a low T50 in the range of from 190° C. to 280° C., a high cetane number in the range of from 31 to 60, and optionally a high distillation curve slope in the range of from 58° C. to 140° C., which combination is effective to afford a combination of the lowest NOx and smoke emissions at the lowest fuel consumption at independent engine control values for the diesel engine that are optimum to afford production of a combination of the lowest NOx and smoke emissions at the lowest fuel consumption, whereby the NOx and smoke emissions from the diesel engine are reduced by at least 10% and 15%, respectively.

Abstract: A method and system for monitoring an exhaust gas adsorber includes a comparison module comparing the first exhaust gas constituent signal corresponding to an amount of exhaust gas constituent in an exhaust conduit and a second exhaust gas constituent signal corresponding to an amount of exhaust gas constituent in the exhaust gas adsorber. The system includes a fault module generating a fault in response to comparing in the comparison module.

Abstract: A method for operating an internal combustion engine (10) for a motor vehicle, said internal combustion engine (10) comprising an exhaust gas system (26) having at least one catalytic converter (28; 30) and at least one lambda probe (38; 40). The internal combustion engine (10) is operated alternately with a lean and a rich fuel-air mixture after a cold start for heating the catalytic converter (28; 30). The lambda probe (40) is heated after the cold start in such a way that it is ready for operation after at most 10 s and the internal combustion engine (10) is operated with a two-level control based on a signal (UL) from the lambda probe (40), such that the change between the operation with lean fuel-air mixture and the operation with rich fuel-air mixture is in each case initiated by the signal (UL) from the lambda probe (40).

Abstract: A method for controlling an internal combustion engine includes monitoring engine operation including a parameter descriptive of NOx generation within the engine, determining a fast transient NOx estimate with a dynamic model based upon the monitored engine operation, and during a fast transient engine operation including an increase in an operating state of the engine and a substantial closing of an exhaust gas recirculation valve, controlling an engine system based upon the fast transient NOx estimate.

Abstract: While the materials compatibility challenges have largely been met in “flex-fuel” vehicles, the engine and aftertreatment operation has not been optimized as function of fuel type (i.e. ethanol, biodiesel, etc.). The full-scale introduction of alternative fuels is most likely going to occur as blends with conventional fuels. This is seen to some extend with the limited introduction of E85 (85% ethanol, 15% gasoline) and B20 (20% biodiesel, 80% conventional diesel.). This further exacerbates the challenge of accommodating variable fuel properties, as there will be differences in combustion properties due to both the type of alternative fuel (i.e. pure biodiesel vs. pure diesel) and blend ratio (i.e. B20 vs. B80). Real-time estimation of the fuel blend is key to the optimized use of two-component fuels (e.g. diesel-biodiesel, gasoline-ethanol, etc.). The approach outlined here uses knowledge of the exhaust composition, fuel and air delivery rates to the engine to estimate the fuel blend.

Abstract: An internal combustion engine, including an air/fuel ratio sensor in an exhaust passage detecting an air/fuel ratio in a heated state, implements a technique improving emission at a starting time, by eliminating splash of water droplets early in the exhaust passage at the starting time to advance the heating starting timing of the air/fuel ratio sensor. At the starting time, opening/closing timing of a valve is advanced from a reference opening/closing timing or the reference of the opening/closing timing of the exhaust valve after the warming-up was ended, which continues until the wall temperature of the exhaust passage near the air/fuel ratio sensor becomes equal to or higher than a water droplet disappearing temperature, at which water droplets disappear. Then, change of the opening/closing timing of the exhaust valve responding to the running state by a variable valve mechanism is started.

Abstract: A fuel control approach that compensates for time delays to increase exhaust gas sensor feedback response speed.

Abstract: An air inlet system of an engine includes a throttle, a fan, a motor, and a throttle sensor. The fan is connected to the throttle. The motor is for driving the fan to force air into at least one intake manifold of the engine through the throttle. The throttle sensor is for controlling the rotational speed of the fan according to the motion of a throttle pedal.

Abstract: When an engine is in a predetermined steady operating state, a gradient accumulation average value ?Aulsa corresponding to the amount of change in the air-fuel ratio AF, detected by an air-fuel ratio sensor, over the period of time from when an upper peak is reached, at which the direction of change in the air-fuel ratio AF is inverted to when a lower peak is reached, at which the subsequent inversion of the direction occurs, is calculated (S100 to S160) and, when the calculated gradient accumulation average value ?Aulsa is greater than a predetermined threshold value ?Aref1 that is determined in advance as an upper limit (absolute value) of the range, in which it may be determined that the air-fuel ratio is even between the cylinders of the engine (S165 to S175), it is determined that the engine is in an air-fuel ratio imbalance state, in which there is an imbalance in air-fuel ratio between the cylinders of the engine.

Abstract: A control system for a turbo charged natural gas engine. A butterfly valve used for fuel control upstream of a carburetor provides non-linear flow response during opening and closing and a flow compensator compensates for the non-linear response. A throttle valve position sensor acts in association with a controller which compares the throttle valve position signal with a predetermined set point and thereby opens or closes the waste gate of the turbo charger which affects oxygen content in the exhaust. A compensator for a throttle valve used with electronic engine controllers is also provided.

Abstract: A method and control system for controlling an engine during diesel particulate filter regeneration includes a diesel particulate filter (DPF) regeneration request module that generates a DPF regeneration request signal. The control system also includes a DPF regeneration control module that controls the oxygen level in the exhaust based on an oxygen level signal corresponding to an oxygen level in the exhaust and a DPF inlet temperature signal corresponding to the DPF inlet temperature.

Abstract: A heating module for an oxygen sensor comprises an estimated mass module, a cumulative mass module, and a temperature control module. The estimated mass module determines an estimated mass of intake air to remove condensation from an exhaust system after startup of an engine. The cumulative mass module determines a cumulative mass of intake air after the engine startup. The temperature control module adjusts a temperature of an oxygen sensor measuring oxygen in the exhaust system to a first predetermined temperature after the engine startup and adjusts the temperature to a second predetermined temperature when the cumulative air mass is greater than the estimated air mass, wherein the second predetermined temperature is greater than the first predetermined temperature.

Abstract: Various systems and methods are described for an exhaust gas sensor coupled to an exhaust system of an engine. One example method comprises, during selected engine fueling conditions, alternating between applying different voltages to the sensor; and identifying an amount of alcohol in fuel injected to the engine based on sensor outputs at the different voltages.

Abstract: Various systems and methods are described for an exhaust gas sensor coupled to an exhaust system of an engine. One example method comprises, during selected engine fueling conditions, alternating between applying first and second voltages to the sensor; and identifying an amount of alcohol in fuel injected to the engine based on sensor outputs at the first and second voltages.

Abstract: A fuel control approach that compensates for time delays to increase exhaust gas sensor feedback response speed.

Abstract: The present invention intends to perform control for detecting a change in air-fuel ratio with high accuracy by an exhaust gas sensor in an internal combustion engine having a turbocharger with a wastegate valve. A control apparatus for an internal combustion engine according to the present invention includes: a turbocharger; a wastegate through which an exhaust gas passes while bypassing a turbine; a wastegate valve for opening/closing the wastegate; an exhaust gas sensor provided in an exhaust passage on the downstream side from the turbine and the wastegate valve; and air-fuel ratio change detection controlling means for executing air-fuel ratio change detection control to change an air-fuel ratio on the upstream side from the turbine and the wastegate valve and detect a change in the air-fuel ratio by the exhaust gas sensor.

Abstract: A system and method are provided for cleaning combustion soot from an exhaust gas aftertreatment sensor. The system and method determine whether to conduct a sensor desoot event, and if it is determined that a sensor desoot event is to be conducted, the exhaust gas temperature is increased such that the temperature of the sensor correspondingly increases to or above a desoot temperature, the exhaust gas temperature is then controlled to maintain the temperature of the sensor at or above the desoot temperature for a predefined time period, and the exhaust gas temperature is then decreased after the temperature of the sensor has been at or above the desoot temperature for the predefined time period.

Abstract: A control apparatus capable of ensuring high control accuracy even if a controlled object is in a transient state, when a control input is calculated based on a value obtained by correcting a value calculated by a feedforward control method using a value calculated by a feedback control method. The control apparatus calculates a fuel correction coefficient such that an output from an oxygen concentration sensor converges to a target output, and multiplies a basic injection amount by the coefficient to calculate a fuel injection amount. The basic injection amount is selected from three values according to the cause of a mapping error. Two of them are calculated by searching respective maps according to corrected throttle valve opening values and engine speed. The other is calculated by multiplying a value obtained by searching a map according to the opening and the speed by a correction coefficient.

Abstract: An engine ECU calculates a rotational variation based on a required rotation time when a complete misfire occurs in a cylinder, a required rotation time when complete combustion occurs in the cylinder, and a required rotation time during the current combustion stroke, and integrates the calculated rotational variation. If it is determined that the number of times the rotational variation has been integrated has reached a predetermined number, the engine ECU calculates an amount of learning value deviation from the integrated rotational variation. If the amount of learning value deviation is equal to or greater than a certain amount, the engine ECU corrects a learning value of a sub-feedback control with respect to the air-fuel ratio.

Abstract: A diagnostic system for an engine includes a stage transition module and a control module. The stage transition module generates a command signal based on a fuel control signal. The command signal commands a fuel system of the engine to intrusively transition between rich and lean states during a diagnostic test that includes first, second, and third stages. The first, second, and third stages are defined based on transitions between the rich and lean states. The control module during the second and third stages detects: an error with a first oxygen sensor based on a comparison between the command signal and a first oxygen signal from the first oxygen sensor; an error with a second oxygen sensor based on a second oxygen signal from the second oxygen sensor; and an error with a catalytic converter based on the first and second oxygen signals and a manifold absolute pressure signal.