A digital filter system is used in an internal combustion engine misfire detection system. The digital filter system includes a signal input for inputting a digital signal generated in response to sensed crankshaft angular velocity. A plurality of digital filters is connected to the signal input, with each of the filters being activated over a predetermined range of engine speeds. Each of the plurality of digital filters, upon being activated, operates as a bandpass filter to filter the digital signal at an engine spatial firing frequency and at a predetermined number of multiples of the engine spatial firing frequency. A signal output is also connected to the plurality of digital filters for outputting the filtered digital signal for engine misfire detection purposes.