Abstract: A NOx sensor diagnostic device includes a NOx sensor disposed in an exhaust passage of an engine, an output value obtaining device for obtaining an output value of the NOx sensor, a spray characteristics changing device for changing spray characteristics for a specific cylinder of cylinders of the engine, and a diagnostic device for diagnosing abnormality of the NOx sensor, based on the output value of the NOx sensor that is changed as a result of the change of the spray characteristics for the specific cylinder by the spray characteristics changing device. An exhaust gas purifying system includes a NOx removal system disposed in an exhaust passage of an engine, a NOx sensor disposed in the exhaust passage at least on an upstream side of the NOx removal system in a flow direction of exhaust air flowing through the exhaust passage, and the NOx sensor diagnostic device.

Abstract: An abnormality detection device determines whether an injection correction amount of each cylinder at the time when maximum rotation numbers are equalized is outside a normal range if the equalization of the maximum rotation numbers among cylinders is completed in an idle stable state. The abnormality detection device determines that an abnormality exists on an injector side if the injection correction amount of a specific cylinder is outside the normal range and a rotation number fluctuation difference of the specific cylinder is in a normal range. The abnormality detection device determines that the abnormality exists on an engine side if the injection correction amount of a specific cylinder is outside the normal range and the rotation number fluctuation difference of the specific cylinder is outside the normal range.

Abstract: A NOx sensor diagnostic device includes a NOx sensor disposed in an exhaust passage of an engine, an output value obtaining device for obtaining an output value of the NOx sensor, a spray characteristics changing device for changing spray characteristics for a specific cylinder of cylinders of the engine, and a diagnostic device for diagnosing abnormality of the NOx sensor, based on the output value of the NOx sensor that is changed as a result of the change of the spray characteristics for the specific cylinder by the spray characteristics changing device. An exhaust gas purifying system includes a NOx removal system disposed in an exhaust passage of an engine, a NOx sensor disposed in the exhaust passage at least on an upstream side of the NOx removal system in a flow direction of exhaust air flowing through the exhaust passage, and the NOx sensor diagnostic device.

Abstract: In a fuel injection system, an ECU judges occurrence of cylinder misfire based on a variation of the number of rotation speed of a diesel engine when an ignition judgment condition is satisfied after the diesel engine starts. If there is a non-ignition cylinder, the increased number of rotation speed of the diesel engine becomes in general smaller than a predetermined value. The ECU gets a common rail pressure corresponding to the non-ignition cylinder, and then judges whether or not a correct pressure variation occurs. The ECU then judges the occurrence of malfunction of the fuel injection valve when the decreased value of the corresponding common rail pressure is out of a normal range, The ECU judges the condition of each cylinder based on the judgment result regarding whether or not the fuel injection valve correctly injects the fuel into the corresponding cylinder.

Abstract: In a fuel amount control apparatus arranged to determine the amount of fuel to be fed to respective cylinders so that the scattering in torque generation throughout the cylinders is suppressed, the amount of correction which is either added to or subtracted from a basic fuel amount, is computed such that a sum total of fuel amount correction factors substantially equals zero. To this end the sum total of the correction factors is first computed and is then checked whether an absolute value of the sum total is greater than a predetermined value. When greater, a given amount is either added to or subtracted from correction factors respectively provided for respective cylinders.

Abstract: Fuel amount control apparatus arranged to determine the amount of fuel to be fed to respective cylinder so that the scattering in torque generation throughout the cylinders is suppressed. Correction amounts are first obtained during idling, and these correction amounts are then modified using at least one engine parameter so that they can be used not only in idle state but also other operating states. To this end, a correction factor is computed using engine speed or the like so as to modify the correction amounts thereby. As a result, a basic fuel amount is corrected by correction factors provided for respective cylinders where the correction factors are further modified to be suitable for any engine operating conditions, providing smooth rotation without uncomfortable vibrations.