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.

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: 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: An apparatus for detecting imbalance abnormality in an air-fuel ratio between cylinders in a multi-cylinder internal combustion engine according to the present invention increases a fuel injection quantity to a predetermined target cylinder to detect imbalance abnormality in an air-fuel ratio between cylinders at least based upon a rotation variation of the target cylinder after increasing the fuel injection quantity. The increase in the fuel injection quantity is carried out in the middle of performing the post-fuel-cut rich control. Since timing of the post-fuel cut rich control is used to increase the fuel injection quantity, the exhaust emission deterioration due to abnormality detection execution can be prevented as much as possible.

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: 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: Provided is an apparatus for detecting cylinder air-fuel ratio imbalance abnormality. The apparatus is provided with an abnormality detecting unit that detects a cylinder air-fuel ratio imbalance abnormality by comparing a value of a parameter correlated with a degree of fluctuation in the air-fuel ratio sensor output to an abnormality threshold value, and a correcting unit that corrects at least one of the value of the parameter or the abnormality threshold value on the basis of atmospheric pressure. An amount of correction performed by the correcting unit is modified according to engine load.

Abstract: An apparatus for detecting an abnormal air-fuel ratio variation, includes an abnormality detecting unit that detects an abnormal variation in each of a plurality of fuel injection valves on the basis of an injection ratio between the plurality of fuel injection valves, a fluctuation in the output before the injection ratio is changed and the fluctuation in the output after the injection ratio is changed; and a setting unit that corrects the abnormality determination threshold for each of the plurality of fuel injection valves on the basis of the injection ratio.

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: An abnormality detection apparatus for a multi-cylinder internal combustion engine changes a fuel injection quantity of a predetermined target cylinder to detect an abnormality of an internal combustion engine based on values of rotational variations relating to the target cylinder detected before and after the change of the fuel injection quantity. The abnormality detection apparatus corrects the values of the rotational variations relating to the target cylinder detected before and after the change of the fuel injection quantity based on at least one of the number of revolutions of the engine and an engine load at a corresponding detection time.

Abstract: In an abnormality detection apparatus and an abnormality detection method for a construction in which each of cylinders is provided with a plurality of fuel injection valves, if it is discerned that a cause of the inter-cylinder variation abnormality exists in one of the fuel injection valves, an air/fuel ratio fluctuation parameter as an index value that represents the degree of the abnormality is calculated by normalizing the air/fuel ratio fluctuation parameter regarding that fuel injection valve on the basis of the injection proportion used when the parameter is measured.

Abstract: A fuel injection amount control apparatus includes an air-fuel ratio sensor which is disposed between an exhaust gas merging portion HK and an upstream catalyst. The control apparatus performs a feedback correction on an amount of fuel to be injected by the fuel injection valve in such a manner that an air-fuel ratio represented by an output value of an upstream air-fuel ratio sensor becomes equal to a target air-fuel ratio which is 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 amount of fuel to be injected by the injection valve in such a manner that an air-fuel ratio becomes a richer air-fuel ratio than the stoichiometric air-fuel ratio as the obtained air-fuel ratio imbalance indicating value becomes larger.

Abstract: The invention provides an inter-cylinder air-fuel ratio imbalance abnormality detection device for a multi-cylinder internal combustion engine, in which when abnormality detection processing of detecting an inter-cylinder air-fuel ratio imbalance abnormality on the basis of revolution speed fluctuations of the multi-cylinder internal combustion engine and ignition timing control for controlling the ignition timing so as to restrict revolution speed fluctuations in the multi-cylinder internal combustion engine are implemented, the implementation of the ignition timing control is restricted when the abnormality detection processing is implemented, and an abnormality detection method to be used in such a device.

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.

Abstract: An apparatus for detecting an abnormal air-fuel ratio variation, includes an abnormality detecting unit that detects an abnormal variation in each of a plurality of fuel injection valves on the basis of an injection ratio between the plurality of fuel injection valves, a fluctuation in the output before the injection ratio is changed and the fluctuation in the output after the injection ratio is changed; and a setting unit that corrects the abnormality determination threshold for each of the plurality of fuel injection valves on the basis of the injection ratio.

Abstract: An abnormality detection apparatus for a multi-cylinder internal combustion engine changes a fuel injection quantity of a predetermined target cylinder to detect an abnormality of an internal combustion engine based on values of rotational variations relating to the target cylinder detected before and after the change of the fuel injection quantity. The abnormality detection apparatus corrects the values of the rotational variations relating to the target cylinder detected before and after the change of the fuel injection quantity based on at least one of the number of revolutions of the engine and an engine load at a corresponding detection time.

Abstract: In an abnormality detection apparatus and an abnormality detection method for a construction in which each of cylinders is provided with a plurality of fuel injection valves, if it is discerned that a cause of the inter-cylinder variation abnormality exists in one of the fuel injection valves, an air/fuel ratio fluctuation parameter as an index value that represents the degree of the abnormality is calculated by normalizing the air/fuel ratio fluctuation parameter regarding that fuel injection valve on the basis of the injection proportion used when the parameter is measured.

Abstract: An apparatus for detecting imbalance abnormality in an air-fuel ratio between cylinders in a multi-cylinder internal combustion engine according to the present invention increases a fuel injection quantity to a predetermined target cylinder to detect imbalance abnormality in an air-fuel ratio between cylinders at least based upon a rotation variation of the target cylinder after increasing the fuel injection quantity. The increase in the fuel injection quantity is carried out in the middle of performing the post-fuel-cut rich control. Since timing of the post-fuel cut rich control is used to increase the fuel injection quantity, the exhaust emission deterioration due to abnormality detection execution can be prevented as much as possible.

Abstract: The invention provides an inter-cylinder air-fuel ratio imbalance abnormality detection device for a multi-cylinder internal combustion engine, in which when abnormality detection processing of detecting an inter-cylinder air-fuel ratio imbalance abnormality on the basis of revolution speed fluctuations of the multi-cylinder internal combustion engine and ignition timing control for controlling the ignition timing so as to restrict revolution speed fluctuations in the multi-cylinder internal combustion engine are implemented, the implementation of the ignition timing control is restricted when the abnormality detection processing is implemented, and an abnormality detection method to be used in such a device.