Method for regenerating a NOX-trap with control of the lambda ratio of the exhaust gas

The fumes generates richness higher than 1 compared to line of exhaust. Evaluating the effective richness of the fumes to the line of exhaust by fuel post injection and adjusting the fumes by controlled fume recirculation. The combustion stability in multicylinder (12) and in the face value are adjusted and measured by pressure reigning in the cylinder/angular information by a target (66) to control the engine (10) rotation. The combustion stability is balanced in advance to the fuel injection.