An apparatus and a method for controlling an internal combustion engine

When an air excess rate is controlled to be reduced based upon an early activation demand of an exhaust gas purification apparatus or a regeneration demand of NOx trap catalyst at a state immediately after an engine has started from at a cold condition, a fuel injection state (injection timing of a main injection, a pilot injection quantity, an injection pressure and so on) from a fuel injection valve is variably controlled so that a crank angle position where a heat generation rate is maximized is kept constant, thereby stabilizing a combustion and preventing combustion fluctuations.