Patent ID: 7654133

Claim:
A malfunction diagnostic apparatus for a combustion improvement device, comprising: a combustion improvement device disposed in an intake passage connected to each of combustion chambers in an internal combustion engine to improve a combustion state; a detector that detects an average crank angular acceleration or a correlated value correlated with the average crank angular acceleration in each of cylinders in the internal combustion engine; an operating state detector that detects a current operating state of the combustion improvement device; and a malfunction determination device that determines whether a malfunction occurs in the combustion improvement device for each of the cylinders, based on the average crank angular acceleration and the current operating state of the combustion improvement device, wherein if the average crank angular acceleration is a negative value in at least one of the cylinders when at least one of the combustion improvement devices for the at least one of the cylinders is operated, the malfunction determination device determines that a malfunction occurs in the at least one of the combustion improvement devices for the at least one of the cylinders in which the average crank angular acceleration is the negative value.