Operating a diesel engine comprises after-injecting fuel temporarily offset from a main injection in a special operation mode so that the injected fuel is combusted with the fuel already dosed and ignited. Preferred Features: A control unit adjusts the injection point of the after-injection for the fuel corresponding to the operational state of the detector. The control unit increases the amount of fuel for the after-injection with simultaneous reduction of the main injection amount during the switching over phase to achieve the after-injection amount. The analogue change of the main injection amount and the after-injection amount is regulated during the switching over phase with consideration of a regulating parameter. The regulating parameter is an induced moment of the diesel engine. Additional fuel is added to the exhaust gas to create the prescribed fuel/air ratio.
