The identification of combustion and detonation in spark ignition (SI) engines is very important to its control within optimized and efficient boundaries. While they are generally identified respectively by phase and knock sensors, this investigation provides additional evidences that the ion current could be used as a sensing device to replace those two sensors, in order to identify both phenomena. The cylinder under combustion could be determined with the ion current signal, by sampling and computing the area under the signal curve. In order to monitor detonation, the correlation between the energy of a frequency band of the ion current signal and the energy of the knock sensor signal was established. The results indicated the viability to use the ion current to detect combustion and detonation in several situations, such as variations in the fuel mixture, mileage of the spark plug, and area size of the spark plug electrode.