A combustion engine has a fuel supply unit, an ignition unit and a controller controlling the amount of fuel and the ignition time. An adjustable throttle element controlling the amount of combustion air to the engine and an adjustable idling stop for the throttle element are provided. The controller includes a regulating unit regulating the rotational speed of the motor to a set-point rotational speed (nsoll) when idling. To adjust the idling stop, the regulating unit is switched off when idling. A diagnostic unit switches off the regulating unit. A method for adjusting a combustion engines provides that the regulating unit is switched off, the amount of fuel supplied is adjusted during idling and a rotational speed is evaluated, and that on the basis of the rotational speed value, it is determined how the idling stop is to be adjusted to reach a set-point rotational speed maximum (nsollmax).