A system and method for operating a combustion engine including a combustion chamber operable in at least a first operating mode and second operating mode. An engine control unit (ECU) performs conductivity sensing within the combustion chamber and interprets the results. Specifically, the ECU determines the current between a pair of spark plug electrodes placed within a combustion chamber of a combustion engine prior to, or after, combustion. The ECU determines whether the current between the pair of electrodes is indicative of spark plug fouling. If spark plug fouling is determined, the ECU can modify the mode of operation to correct the spark plug fouling and clean the deposits on the spark plug while the engine is in operation and without operation intervention.