Abstract: When a request for temperature increase of a three-way catalyst is made, a CPU executes dither control in which one of a plurality of cylinders is set as a rich combustion cylinder with a richer air-fuel ratio than a stoichiometric air-fuel ratio and the remaining cylinders are set as lean combustion cylinders with a leaner air-fuel ratio than the stoichiometric air-fuel ratio. When not executing the dither control, the CPU learns a rich learning value that is a learning value of a degree of a rich imbalance based on an upstream-side air-fuel ratio. When the rich learning value is greater than or equal to a predetermined value, the CPU prohibits the dither control.

Abstract: A fuel injection controller for an internal combustion engine selects as the injection mode either single injection or split injection, counts, based on a drive current detection signal, which indicates that a drive current is generated to be fed to the direct injector, the number of occurrences of the drive current in one combustion cycle as a number-of-injections count value, and determines, based on the number-of-injections count value, whether the combustion state in the cylinder is satisfactory. The fuel injection controller determines that the combustion state in the cylinder is unsatisfactory if the number-of-injections count value in one combustion cycle is one when catalyst warm-up control is being performed with the temperature of the engine being lower than or equal to a predetermined temperature.

Abstract: When a request for temperature increase of a three-way catalyst is made, a CPU executes dither control in which one of a plurality of cylinders is set as a rich combustion cylinder with a richer air-fuel ratio than a stoichiometric air-fuel ratio and the remaining cylinders are set as lean combustion cylinders with a leaner air-fuel ratio than the stoichiometric air-fuel ratio. When not executing the dither control, the CPU learns a rich learning value that is a learning value of a degree of a rich imbalance based on an upstream-side air-fuel ratio. When the rich learning value is greater than or equal to a predetermined value, the CPU prohibits the dither control.

Abstract: A control device of an internal combustion engine according to the present invention executes air-fuel ratio control based on an output of an air-fuel ratio sensor provided at an upstream side of a catalyst, with correction based on an output of an oxygen sensor at a downstream side of the catalyst. When it is determined that a degree of an output tendency in a predetermined lean region is not less than a predetermined lean degree, and that a degree of an output tendency in a predetermined rich region is less than a predetermined rich degree based on lean tendency and rich tendency values representing output tendencies of the oxygen sensor, a limit is set to the correction in a direction to more suppress enriching of an air-fuel ratio as a degree is larger in which the output of the oxygen sensor is shifted to a lean side.

Abstract: A fuel injection controller for an internal combustion engine selects as the injection mode either single injection or split injection, counts, based on a drive current detection signal, which indicates that a drive current is generated to be fed to the direct injector, the number of occurrences of the drive current in one combustion cycle as a number-of-injections count value, and determines, based on the number-of-injections count value, whether the combustion state in the cylinder is satisfactory. The fuel injection controller determines that the combustion state in the cylinder is unsatisfactory if the number-of-injections count value in one combustion cycle is one when catalyst warm-up control is being performed with the temperature of the engine being lower than or equal to a predetermined temperature.

Abstract: A grille shutter is a device configured to adjust a temperature of coolant water of an engine by adjusting an amount of outside air introduced into a radiator of the engine. An ECU performs a failure diagnosis for the engine based on a temperature of coolant water of the engine. When the grille shutter is immovable in an opened state of the grille shutter regardless of an operating command to the grille shutter, the ECU renders the failure diagnosis process for the thermostat valve not to be executed. As a result, an incorrect operation of various controls executed based on a temperature of coolant water of the engine can be suppressed.

Abstract: In a vehicle provided with an engine, an EGR cooler for cooling EGR gas recirculated from an exhaust channel of the engine to an intake channel thereof by using a coolant, an electric pump for supplying the coolant to the EGR cooler, and a gas temperature sensor for detecting the temperature of the EGR gas temperature at the downstream of the EGR cooler, an ECU acquires a first gas temperature in a normally stable state where the electric pump is rotating, thereafter performs a coolant amount suppressing process to suppress the rotational speed of the electric pump, acquires a second gas temperature in a suppressed stable state after a predefined time has elapsed from the start of the coolant amount suppressing process, and determines that the EGR cooler is abnormal if a difference between the first gas temperature and the second gas temperature is less than a threshold value.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine is provided. A controller is programmed to perform correction amount guard control allowing adjustment of a correction amount by setting a limit on the correction amount when an appearance frequency of a state where an output value from a downstream sensor is leaner than a predetermined value is equal to or higher than a predetermined value. When a state where the output value from the downstream sensor is leaner than the predetermined value lasts for a duration equal to or longer than a predetermined time, an incorporation speed at which, during learning control, the correction amount for sub feedback control is incorporated into a learning value is set to a larger value that when the duration is shorter than the predetermined time, and performance of the correction amount guard control is suppressed until the learning control is completed.

Abstract: A fuel injection amount control apparatus comprises an air-fuel ratio sensor disposed between an exhaust gas merging portion and an upstream catalyst. The control apparatus performs a feedback correction on an amount of fuel to be injected by the fuel injection valve so that an air-fuel ratio represented by the output value of the upstream air-fuel ratio sensor becomes equal to a target air-fuel ratio set at stoichiometric air-fuel ratio. The control apparatus obtains an air-fuel ratio imbalance indicating value, which becomes larger as a difference in air-fuel ratio of each of the mixtures supplied to each of the combustion chambers among the cylinders becomes larger, and performs an increasing correction to the instructed fuel injection amount in such a manner that an air-fuel ratio determined by the instructed fuel injection amount becomes richer than the stoichiometric air-fuel ratio as the obtained air-fuel ratio imbalance indicating value increases.

Abstract: An ECU sets a leakage flow rate flowing through a radiator circulation passage in a closed state of a thermostat valve, calculates an estimated temperature of coolant water in the radiator circulation passage based on a set leakage flow rate and a detected water temperature of an engine-side coolant water temperature sensor, and performs a failure diagnosis for the thermostat valve based on a difference between the calculated estimated temperature and the detected water temperature of the radiator-side coolant water temperature sensor. The leakage flow rate during operation of the electric pump is set to be a larger value as compared to the leakage flow rate during stopping of the pump. As a result, a diagnostic can be prevented by improving an accuracy of failure detection for the thermostat valve.

Abstract: A learning unit learns a difference between a detected value ECT and a detected value RCT when it is determined that the detected value ECT and detected value RCT are stable while an engine is at a stop. A diagnostic unit performs a fault diagnosis for the engine based on the difference between the detected value ECT and detected value RCT having been corrected through use of a learned value learned by the learning unit. Accordingly, a fault diagnostic system for an internal combustion engine and a fault diagnostic method for an internal combustion engine can be achieved in which accuracy in fault diagnosis for the internal combustion engine can be improved and an erroneous diagnosis can be restrained.

Abstract: In a vehicle provided with an engine, an EGR cooler for cooling EGR gas recirculated from an exhaust channel of the engine to an intake channel thereof by using a coolant, an electric pump for supplying the coolant to the EGR cooler, and a gas temperature sensor for detecting the temperature of the EGR gas temperature at the downstream of the EGR cooler, an ECU acquires a first gas temperature in a normally stable state where the electric pump is rotating, thereafter performs a coolant amount suppressing process to suppress the rotational speed of the electric pump, acquires a second gas temperature in a suppressed stable state after a predefined time has elapsed from the start of the coolant amount suppressing process, and determines that the EGR cooler is abnormal if a difference between the first gas temperature and the second gas temperature is less than a threshold value.

Abstract: An abnormality detecting device of an internal combustion engine according to the present invention includes a sensor nick abnormality detecting unit configured to detect a nick abnormality in a detecting element of a downstream side sensor which is provided in a downstream side of an exhaust gas purifying catalyst in an exhaust passage and generates an output corresponding to an oxygen concentration in exhaust gas, on the basis of a matter that a distribution of an output of the downstream side sensor is biased to an area in which the air-fuel ratio is leaner than a theoretical air-fuel ratio, and an inhibiting unit configured to inhibit detection of the nick abnormality of the detecting element by the sensor nick abnormality detecting unit in the case that an intake air amount exceeds a predetermined amount.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine is provided. A controller is programmed to perform correction amount guard control allowing adjustment of a correction amount by setting a limit on the correction amount when an appearance frequency of a state where an output value from a downstream sensor is leaner than a predetermined value is equal to or higher than a predetermined value. When a state where the output value from the downstream sensor is leaner than the predetermined value lasts for a duration equal to or longer than a predetermined time, an incorporation speed at which, during learning control, the correction amount for sub feedback control is incorporated into a learning value is set to a larger value that when the duration is shorter than the predetermined time, and performance of the correction amount guard control is suppressed until the learning control is completed.

Abstract: A control device of an internal combustion engine according to the present invention executes air-fuel ratio control based on an output of an air-fuel ratio sensor provided at an upstream side of a catalyst, with correction based on an output of an oxygen sensor at a downstream side of the catalyst. When it is determined that a degree of an output tendency in a predetermined lean region is not less than a predetermined lean degree, and that a degree of an output tendency in a predetermined rich region is less than a predetermined rich degree based on lean tendency and rich tendency values representing output tendencies of the oxygen sensor, a limit is set to the correction in a direction to more suppress enriching of an air-fuel ratio as a degree is larger in which the output of the oxygen sensor is shifted to a lean side.

Abstract: A control device of an internal combustion engine according to the present invention has units configured to inject fuel at a first predetermined ratio from first and second fuel injection valves which are provided in each of cylinders to calculate a first value indicating a degree of variation in air-fuel ratios between the cylinders based on a output of the engine, and inject fuel at a second predetermined ratio therefrom to calculate a second value in the same manner. Furthermore, the control device has a unit configured to select one mode from modes relating to abnormality in the first fuel injection valve or the second fuel injection valve on the basis of the first and second values, and calculate a value indicating the degree of the variation in the air-fuel ratios between the cylinders, thereby calculating a fuel amount of the basis of them.

Abstract: An inter-cylinder air-fuel ratio variation abnormality detection apparatus is disclosed. The apparatus determines imbalance of an air-fuel ratio among the cylinders based on a difference between index values correlated with crank angular velocities detected in a set of opposite cylinders belonging to different banks and having crank angles different from one another by 360°; and carries out an air-fuel ratio feedback process for controlling an amount of injected fuel for each of the banks, wherein the apparatus comprises a correction unit correcting, before determining the air-fuel ratio imbalance, the difference between the index values in a direction of combustion improvement for opposite cylinders that are opposite to cylinders belonging to a bank identical to a bank of a cylinder with the most deviating index value from a standard value among all the cylinders and being other than the cylinder with the most deviating index value.

Abstract: A grille shutter is a device configured to adjust a temperature of coolant water of an engine by adjusting an amount of outside air introduced into a radiator of the engine. An ECU performs a failure diagnosis for the engine based on a temperature of coolant water of the engine. When the grille shutter is immovable in an opened state of the grille shutter regardless of an operating command to the grille shutter, the ECU renders the failure diagnosis process for the thermostat valve not to be executed. As a result, an incorrect operation of various controls executed based on a temperature of coolant water of the engine can be suppressed.

Abstract: An ECU performs a failure diagnosis for a thermostat valve after starting of an engine based on an output of an engine-side coolant water temperature sensor and an output of a radiator-side coolant water temperature sensor. When an electric pump operates in accordance with a heating request or the like of an air-conditioning device during stopping of the engine, the thermostat valve attains a closed state. When the electric pump operates during stopping of the engine before the current starting of the engine, starting of the failure diagnosis performed after starting of the engine is delayed as compared to the case where the electric pump does not operate during stopping of the engine. Consequently, erroneous determination can be suppressed in the failure diagnosis for the thermostat valve.

Abstract: The leakage diagnosis that carries out a leakage diagnosis on the basis of an internal pressure state of an airtight compartment by emitting gas from the compartment via a canister during a stop of the internal combustion engine includes; detecting a physical quantity that reflects a fuel adsorption state of the canister; and repeating the leakage diagnosis within the number of times of the leakage diagnosis, limited on the basis of the detected physical quantity. The compartment is formed in an evaporative fuel processing mechanism for an internal combustion engine. The evaporative fuel processing mechanism includes a fuel tank.