Abstract: A malfunction diagnosis apparatus diagnoses a malfunction of an exhaust gas sensor provided on a downstream side of a catalyst. A dead time determination unit determines a dead time between a first time point, at which fuel cut of the internal combustion engine is started, and a second time point, at which the fuel cut starts exerting effect on an output of the exhaust gas sensor. An output change time measurement unit measures an output change time between the first time point and a third time point, at which the output of the exhaust gas sensor changes to a leaner side than a threshold. A malfunction determination unit determines whether a malfunction is caused in the exhaust gas sensor on the basis of a response time of the exhaust gas sensor obtained by subtracting the dead time from the output change time.

Abstract: An engine controller is applied to a system that includes an engine and an exhaust purifying catalyst for purifying exhaust gas of the engine. The engine controller has an idle stopping means, a catalyst temperature detecting means and an engine restarting means. The idle stopping means stops the engine when a predetermined idle stop condition is satisfied. The catalyst temperature detecting means detects a temperature of the exhaust purifying catalyst while the engine is stopped by the idle stopping means. The engine restarting means restarts the engine when the temperature of the exhaust purifying catalyst, which is detected by the catalyst temperature detecting means, becomes equal to or lower than an engine restart determination temperature, which is determined on a basis of an activation temperature of the exhaust purifying catalyst.

Abstract: A malfunction diagnosis apparatus diagnoses a malfunction of an exhaust gas sensor provided on a downstream side of a catalyst. A dead time determination unit determines a dead time between a first time point, at which fuel cut of the internal combustion engine is started, and a second time point, at which the fuel cut starts exerting effect on an output of the exhaust gas sensor. An output change time measurement unit measures an output change time between the first time point and a third time point, at which the output of the exhaust gas sensor changes to a leaner side than a threshold. A malfunction determination unit determines whether a malfunction is caused in the exhaust gas sensor on the basis of a response time of the exhaust gas sensor obtained by subtracting the dead time from the output change time.

Abstract: ECU calculates variations of air-fuel ratios of respective cylinders and variations of air-fuel ratios of all the cylinders in variable intake valve lift devices of two cylinder groups. Presence and absence of an abnormality is determined on the basis of whether ratios of variations of air-fuel ratios of respective cylinders to variations of air-fuel ratios of all the cylinders are less than an abnormality threshold. Whether which of variable intake valve lift devices of the cylinder groups is abnormal is determined from control modes of the variable intake valve lift devices of the respective cylinder groups, and the relationship between that cylinder group, to which a cylinder being maximum in air-fuel ratio belongs, and cylinder group, to which a cylinder being minimum in air-fuel ratio belongs.

Abstract: ECU calculates variations of air-fuel ratios of respective cylinders and variations of air-fuel ratios of all the cylinders in variable intake valve lift devices of two cylinder groups. Presence and absence of an abnormality is determined on the basis of whether ratios of variations of air-fuel ratios of respective cylinders to variations of air-fuel ratios of all the cylinders are less than an abnormality threshold. Whether which of variable intake valve lift devices of the cylinder groups is abnormal is determined from control modes of the variable intake valve lift devices of the respective cylinder groups, and the relationship between that cylinder group, to which a cylinder being maximum in air-fuel ratio belongs, and cylinder group, to which a cylinder being minimum in air-fuel ratio belongs.