Abstract: A method of synchronizing a crankshaft signal with the stroke cycle of a four-stroke internal combustion engine induces misfiring in a specified engine cylinder, and uses an assumed synchronization to identify the misfiring cylinder. The crankshaft signal is used to identify reference angular positions of the crankshaft intermediate top dead center positions of consecutive cylinders of the engine firing order, and a time difference between successive reference positions is determined. When the assumed synchronization is such that the current rotation of the crankshaft includes the cylinder in which misfiring is induced, the determined time difference is accumulated in a first accumulator; otherwise, the determined time difference is accumulated in a second accumulator. The presence of misfiring causes the two accumulators to diverge in value, and the direction of such divergence is used to determine if the assumed synchronization is correct or incorrect.

Abstract: A method of synchronizing a crankshaft signal with the stroke cycle of a four-stroke internal combustion engine induces misfiring in a specified engine cylinder, and uses an assumed synchronization to identify the misfiring cylinder. The crankshaft signal is used to identify reference angular positions of the crankshaft intermediate top dead center positions of consecutive cylinders of the engine firing order, and a time difference between successive reference positions is determined. When the assumed synchronization is such that the current rotation of the crankshaft includes the cylinder in which misfiring is induced, the determined time difference is accumulated in a first accumulator; otherwise, the determined time difference is accumulated in a second accumulator. The presence of misfiring causes the two accumulators to diverge in value, and the direction of such divergence is used to determine if the assumed synchronization is correct or incorrect.