A system for controlling an internal combustion engine has an in-cylinder pressure sensor, a crank angle sensor and a controller coupled to receive inputs from the pressure sensor and crank angle sensor. The controller is configured to convert the cylinder pressure input into a combustion metric indicative of the combustion occurring in the measured cylinder and control fuel input and timing into the engine based on the combustion metric. The controller samples the in-cylinder pressure sensor at a high frequency during critical combustion events and at a lower frequency during the non-critical cylinder conditions.