Abstract: A method and device for monitoring the functionality of a valve stroke adjusting device of an internal combustion engine in a cold start phase. The internal combustion engine includes an electronically controllable throttle, the control utilizing an integral component to control the throttle, and the functionality is monitored by determining the integral component in a cold start phase, comparing the integral component with at least one predetermined threshold value and evaluating the functionality of the valve stroke adjusting device on the basis of the comparison.

Abstract: An air guiding system is provided for an internal-combustion engine of a piston-type construction and includes an air filter and a feeding device for a suction system connected with cylinders of the internal-combustion engine. A receptacle, through which air flows, is arranged in a pipe between the air filter and the feeding device for influencing resonances. For optimizing the sound characteristics of the internal-combustion engine, the pipe is interrupted in the area of the receptacle, and a cross-section of the receptacle is larger than the cross-section of pipe sections of the pipe extending to the receptacle.