Method of operating a combustion engine

A method of operating a combustion engine is described. The combustion engine comprises a cylinder, a piston, an injection valve and a pressure sensor, wherein the cylinder and the piston delimit a combustion chamber. The method comprises injecting fuel with the injection valve into the combustion chamber according to an injection signal (TI) and measuring a pressure signal (P) in the combustion chamber with the pressure sensor. The method comprises the further steps of: determining an actual value (Va1) of a heat release rate peak (HRRP1) depending on the pressure signal (P), determining a difference between the actual value and a corresponding nominal value, and adapting the injection signal (TI) depending on the difference.