A process and a system for preventing pre-ignition in an internal combustion engine (ICE) includes detecting an ionization level of a combusted gas from a cylinder of the ICE during gas exchange and for a given combustion cycle i. When the ionization level is greater than a reference ionization level a pre-ignition countermeasure prior to and/or during an immediate subsequent combustion cycle i+1 is executed. The ionization sensor may be part of a spark initiating device of the ICE or be a separate ionization sensor.