Accurate detection of abnormal combustion is enabled even in an engine such that the combustion chamber is provided with only one ignition plug with an ion current detection function. An engine control system according to the present invention is provided with: an ion detection device (4) that detects ions produced during combustion; and a control device (20) that includes a combustion state determination unit that determines whether the combustion state in the engine is normal combustion or abnormal combustion on the basis of the time (&Dgr;t) between the fall of an engine ignition control signal (4h) and the rise of an ion signal (4g) outputted from the ion detection device.
