A method for efficiently determining whether a distributorless or hybrid ignition system is the origin of engine problems by consecutively disconnecting and reconnecting the primary connector from each coil of the ignition system. Once a single primary connector is disconnected from a coil and engine misfiring or roughness declines, the problem cylinder pair has been located. The method further includes measuring the firing line voltage of accessible spark plug wires for each cylinder to identify a single faulty cylinder, that may now be serviced.