An engine ignition and control system for an internal combustion engine. The system includes an ignition transformer mounted directly to a spark plug and adapted to rapidly re-fire the spark plug during a combustion cycle enabling e.g. multispark ignition during adverse engine operating conditions and here the performance of various ignition diagnostic procedures. A controller provides signals to a circuit which causes charging of the transformer for ignition and subsequent charging of the transformer for diagnostic purposes. The system also includes a diagnostic circuit, connected to the transformer, which can detect the occurrence of electrical discharges across the spark plug electrodes as a result of the diagnostic charges. The detection circuit either outputs a signal or omits a signal to the controller which allows the controller to diagnose conditions within the combustion cylinder such as misfire, autoignition or preignition. Additionally, the diagnostic circuit is capable of outputting a signal which can be correlated to the load on the engine.