Vehicle longitudinal motion is decisively influenced by engine-control functions. The dynamics of the mixture formation in particular can lead to uncontrolled variations in the air/fuel ratio. This has a considerable adverse effect on ride comfort as well as exhaust emissions. Changes in the indicated torque following a throttle alteration are analysed, reaction sequences differing in time response are separated. Physics-based control functions can thus be established, achieving better results than a purely empirical method.