Plasma electronic ignition system for an internal combustion engine having a drive shaft and at least one cylinder, said system being configured to generate within said engine cylinder a spark of predetermined duration and comprising: - an ignition coil provided with at least a primary winding and a secondary winding, wherein said at least a primary winding is connectable, by means of an electrical connection, to a voltage generator device and said secondary winding is connectable to a spark plug; - a switch connected to said primary winding and drivable to open and/or close it according to the value of a driving signal, in order to prevent or allow a passage of electric current through said primary winding, respectively; - a control unit associated with said switch and configured to drive it to an open and/or closed position according to the value of said driving signal; said control unit comprising hardware and software means configured to control said switch by varying its timing and/or the period of opening and closing so that said switching generates, in the secondary winding, an oscillating electric potential adapted to generate and/or maintain active at least an electric arc at the terminals of a discharge gap of the spark plug; wherein it comprises a measuring device of a parameter representing a ionization process at said discharge gap of the spark plug associated with said secondary winding and arranged to detect a current value in said secondary winding and to send a signal representative of said value to the control unit; said control unit being configured to activate said measuring device upon the shutdown of said electric arc, wherein the control unit is configured for: - charging said primary winding by means of a closing of said switch for a predetermined first time interval; - powering said secondary winding by electromagnetic induction by means of an opening of said switch in order to generate a spark at said spark plug; - subsequent alternate succession of openings and closings of said switch to modulate a duration of said spark; characterized in that the control unit is configured for: - detecting the angular position of the drive shaft during each revolution; - opening said switch to cancel the voltage on said secondary winding by extinguishing said spark when said angular position corresponds to a preset reference value for said cylinder; - detecting the ionization current as a result of said opening; - further charging of said primary winding and further powering of said secondary winding via electromagnetic induction, if the ionization current detected is lower than a preset reference value or close to zero, in order to avoid the unburnt mixture reaching the exhaust pipe. - an ignition coil provided with at least a primary winding and a secondary winding, wherein said at least a primary winding is connectable, by means of an electrical connection, to a voltage generator device and said secondary winding is connectable to a spark plug; - a switch connected to said primary winding and drivable to open and/or close it according to the value of a driving signal, in order to prevent or allow a passage of electric current through said primary winding, respectively; - a control unit associated with said switch and configured to drive it to an open and/or closed position according to the value of said driving signal; said control unit comprising hardware and software means configured to control said switch by varying its timing and/or the period of opening and closing so that said switching generates, in the secondary winding, an oscillating electric potential adapted to generate and/or maintain active at least an electric arc at the terminals of a discharge gap of the spark plug; - charging said primary winding by means of a closing of said switch for a predetermined first time interval; - powering said secondary winding by electromagnetic induction by means of an opening of said switch in order to generate a spark at said spark plug; - subsequent alternate succession of openings and closings of said switch to modulate a duration of said spark; - detecting the angular position of the drive shaft during each revolution; - opening said switch to cancel the voltage on said secondary winding by extinguishing said spark when said angular position corresponds to a preset reference value for said cylinder; - detecting the ionization current as a result of said opening; - further charging of said primary winding and further powering of said secondary winding via electromagnetic induction, if the ionization current detected is lower than a preset reference value or close to zero, in order to avoid the unburnt mixture reaching the exhaust pipe.