the other cylinders will operate at increased load to compensate for the torque demand and at the same time there is a risk of exceeding the maximum allowable particulate filter temperatures in regeneration mode a stuck open injector failure will result in increased hydrocarbon and carbon monoxide emissions and will risk exceeding maximum allowable oxidation catalyst and particulate filter temperatures consequently a misfire diagnostic operating in system 10 is adapted to determine when the engine is misfiring to locate the misfiring cylinder or cylinders to count and record the misfiring events and to provide the on board diagnostic with a warning flag in case of repeated misfire events any of these conditions would signal the necessity for engine service or to stop engine operation to prevent catalyst damage the misfire detection diagnostic is designed to meet u s obdii and eobd requirements embodiments of the misfire detection method described herein may employ a discrete fourier transformation dft of a crankshaft oriented speed signal particularly the method involves assessment of the statistical behavior of a phase component of one or more selected corresponding dft derived harmonic orders during normal non misfire operation the engine is always represented by a randomly distributed phase component in the dft produced frequency domain while a misfire of a single cylinder or misfire of any cylinder pair results in u201c locked u201d phase of the misfire indicative harmonic order it must be noted that misfire free operation produces a low.