Patent ID: 6725709
Filing Date: 2004-04-27
Classification: G01M

Abstract:
A combustion state diagnosing system for diagnosing a combustion state of a multiple-cylinder engine by measuring a parameter of the combustion state varying according to the combustion state of the engine and diagnosing the combustion state on the basis of the parameter of the combustion state, comprising:a combustion state parameter measuring means which measures values of the parameter of the combustion state N times (at least once) in one ignition cycle of the multiple cylinder engine at times corresponding to a predetermined crank angle; a specific rotation period component extracting means for extracting a specific rotation period component of a period synchronous with rotation of a crankshaft from values of the parameter of the combustion state measured by the combustion state parameter measuring means at least in two rotations of a crankshaft; and a combustion state judging means for judging the combustion state on the basis of the specific rotation period component extracted by the specific rotation period component extracting means to detect low frequency cylinder misfiring.