Abstract: A misfire detection assembly, used in conjunction with a motor vehicle having a fuel injector, an internal combustion engine and at least one output sensor, includes: a correlator which is electrically connected to the fuel injector and the output sensor wherein the correlator correlates firing events created by the fuel injector with an output signal created by the output sensor; a filter electrically connected to the correlator to receive the output signal and to compare the output signal against a variable threshold signal created by the filter; and a recorder, electrically connected to the filter, to record the firing events which exceed the variable threshold signal and those which do not exceed the variable threshold signal.

Abstract: Misfiring of individual cylinders in an internal combustion engine 70 is detected based on simultaneous use of two or more different methods of misfire detection which examine different combustion-related parameters of engine operation, such as crankshaft acceleration and exhaust gas pressure. An analyzer 76 produces a final misfire determination M.sub.f (i) based on the simultaneously obtained misfire determinations in order to provide greater coverage of the speed-load range of engine 70 and to provide increased confidence and accuracy in calling misfires in the portion of the speed-load range where both misfire methods are presumed to function.

Abstract: A system and method for processing test measurements collected from an internal combustion engine that is cold-tested for diagnostic purposes. Test measurements are collected from an engine. The test measurements are "pre-processed" by filtering and subsampling techniques so that Principle Component Analysis can be applied to condense the quantity of test measurements while still retaining a statistically accurate indication of a majority of the original measurements. The pre-processed test measurements are then passed through one or more classifiers including: a Neural Network classifier, a Fuzzy Logic classifier, a cluster-based classifier (or "Spherical" classifier) and a Genetic Program classifier. Results from these classifiers can be used to obtain a verdict about an engine (i.e., whether the engine is "normal" or "faulty").

Abstract: Misfiring of individual cylinders in an internal combustion engine is detected based on sensing exhaust pressure during each operating cycle of the engine. A pressure signal is sampled and digitized during each cycle to form an input vector for a pattern classifier. Predetermined internal coefficients of the trained classifier enable the classifier to discriminate between firing and misfiring cylinders in real time with a high degree of accuracy. Overall system cost is reduced by sharing a pressure transducer with an exhaust gas recirculation system on the internal combustion engine.