ABNORMALITY DETECTION DEVICE FOR INTERNAL COMBUSTION ENGINE

A malfunction detecting device for an internal combustion engine is mounted on a vehicle and includes an engine and a control unit. The engine is a multi-cylinder engine and is a bifuel-enabled engine which is capable of switching plural kinds of fuels including a gas f uel and which can use biofuel, The control unit detects, in case of detecting a malfunction with respect to an imbalance of an air fuel ratio among the cylinders at a time of an operation based on the gas fuel, the malfunction based on a rotational speed variation of the engine and/or a variation of pressure pulsations of the gas fuel due to a fuel injection.