Device for detecting continuous misfires of a multi-cylinder internal combustion engine

A device for detecting continuous misfires of a multi-cylinder internal combustion engine, comprising:

• crank angle detector means for detecting predetermined crank angles of said internal combustion engine corresponding to predetermined phase angles of a plurality of cylinders of said internal combustion engine;
• timer means, coupled to said crank angle detector means, for determining lengths of time between said predetermined crank angles of said internal combustion engine;
• angular acceleration detector means, coupled to said timer means, for determining angular acceleration of a crankshaft of said internal combustion engine over predetermined phase intervals of said plurality of cylinders;
• an acceleration differential calculator for calculating an acceleration differential between an angular acceleration corresponding to each of said plurality of cylinders and a respective other one of said plurality of cylinders;
• variance determining means, coupled to said acceleration differential calculator, for determining a variance of levels of said acceleration differential over ignition timings of two cylinders which are separated by a predetermined crank angle;
• and
• comparator means, coupled to said variance determining means, for comparing said variance with predetermined misfire judgment reference level, for detecting an occurrence of continuous misfires when said variance is less than said misfire judgment reference level.