Patent ID: 7530261
Filing Date: 2009-05-12
Classification: G01M

Abstract:
1. A method for misfire detection in an internal combustion engine system, comprising the steps of: producing a first signal corresponding to rotational characteristics of an engine crankshaft taken at selected times, said first signal including a measure of variability corresponding to characteristics unique to the internal combustion engine system irrespective of misfire; converting the first signal into a frequency-domain misfire detection metric having components selected from an engine cycle frequency and harmonic orders thereof; normalizing said misfire detection metric using a non-misfire metric corresponding to a non-misfire operating condition of the internal combustion engine system to remove said measure of variability; detecting a misfire condition when the normalized misfire detection metric satisfies a predetermined threshold; identifying one of (i) an individual cylinder and (ii) multiple cylinders that misfired when said misfire condition is detected as a function of a calculated phase.