Abstract: A regulating device is described for regulating or adjusting the composition of the operating mixture of an internal combustion engine. When the engine or exhaust gas probe is still cold, the composition of the fuel-air mixture is controlled in an open-loop manner, and upon the attainment of a minimum operating temperature, the closed-loop regulating device for influencing the fuel-air mixture is activated. The activation of the regulating device is effected, when the engine is being operated under a load, after the attainment of a first, low temperature value; during engine idling, this is effected after the attainment of a second, higher temperature value. Via the throttle valve, a switchover is effected between two threshold values of a threshold switch.