The invention concerns a method for controlling at least one of a fuel supply and an air supply to an internal combustion engine (1), in a fuel supply section thereof, such that an A/F-ratio is adjusted automatically to a desired level. Moreover, the method is activated at a speed close to a cut-out speed threshold (52) where the engine speed will fluctuate around the threshold (52) and the method comprises the steps of: receiving engine speed data on rotational speed from the engine (1), briefly changing the A/F ratio, comparing engine speed data that are essentially unaffected by the brief change to engine speed data that are affected by the brief change to evaluate the impact on the engine speed fluctuation resulting from the brief change, adjusting the A/F ratio in the same direction as the brief change if the engine speed data affected by the brief change indicates an increase in acceleration after combustion/s, and adjusting the A/F ratio in the opposite direction to the brief change if the engine speed data affected by the brief change indicates a decrease in acceleration after combustion/s.