A method for controlling fuel injection of a combustion engine and a corresponding system includes providing at least a first predetermined air-fuel mixture map and determining a first air-fuel ratio based on at least one engine operating parameter and the at least first predetermined air-fuel mixture map; determining a second air-fuel ratio that is offset with a first constant value from the first air-fuel ratio, determining if a first operating mode or a second operating mode is selected; controlling engine fuel injection according to the first air-fuel ratio when a currently requested fueling rate results in a smaller air-fuel ratio than the first air-fuel ratio and the first operating mode is selected; or alternatively controlling engine fuel injection according to the second air-fuel ratio when a currently requested fueling rate results in a smaller air-fuel ratio than the second air-fuel ratio and the second operating mode is selected.