Adaptive method for detecting misfire in an internal combustion engines using an engine-mounted accelerometer

An adaptive method for detecting misfire in a combustion chamber of a piston and cylinder assembly for a spark-ignition, automotive, internal combustion engine, the engine having a cylinder housing, a crankshaft and a camshaft, an accelerometer being mounted on the exterior of the cylinder housing;

• the method comprising the steps of:
• measuring engine combustion vibration energy in a frequency range of about 2 KHz to 4.5 KHz by recording and processing accelerometer output data to detect whether a misfire has occurred;
• measuring instantaneous crankshaft and camshaft positions;
• determining the location in the combustion cycle at which combustion is expected to occur using instantaneous crankshaft position and camshaft angle data;
• determining whether combustion has occurred using accelerometer output data;
• determining instantaneous crankshaft acceleration using crankshaft position data;
• determining whether combustion has occurred using crankshaft acceleration data, and;
• determining whether a misfire in the combustion chamber is detected by comparing processed accelerometer output data with processed crankshaft position data and signaling a misfire if the processed accelerometer output data and the processed crankshaft position data both indicate a misfire.