US Patent 7882730 Internal-combustion-engine ignition diagnosis apparatus

There is provided an ignition diagnosis apparatus that detects ignition abnormality in a multi-point-ignition internal combustion engine. An ion detection device provided in at least one of a plurality of ignition devices detects an electric quantity based on ions produced in a combustion chamber due to combustion of an inflammable fuel-air mixture; an ion occurring timing detection device detects an ion occurring timing, based on the electric quantity detected in a predetermined detection period; an ignition abnormality determination device compares the detected ion occurring timing with a comparison timing set in such a way as to be delayed in terms of the rotation angle of a crankshaft of the internal combustion engine with respect to an ignition timing set for the ignition device provided with the ion detection device, and determines that ignition performed by the ignition device provided with the ion detection device is abnormal, in the case where the ion occurring timing is delayed in terms of the rotation angle of the crankshaft with respect to the comparison timing.