Method for controlling an internal combustion engine

A method of operating an internal combustion engine with a direct injection system controlled by an engine control unit (ECU) is described. The ECU comprises a flow curve table storing data indicative of fuel quantities vs. injector pulse widths. The method comprises an injector learning event during which actual fuel values related to a fuel injector are determined, said injector learning event being enabled during an idle or deceleration condition of said engine and comprising the steps of: operating the engine into a homogeneous combustion mode; and concurrently degrading the combustion and/or splitting the injection pulses while monitoring the combustion performance to determine learned fuel data.