Abstract: An improved air intake arrangement for Diesel engine in which an intake air shutter valve is provided in an intake air passage of the engine for closing the intake air passage when the degree of depression of an accelerator pedal is small, especially in engine idling and speed retardation, i.e. during non-load period, so as to reduce engine vibrations and noises during light-load operation by throttling the intake air passage or reducing the substantial effective passage area, and also deterioration of combustion is prevented by reducing throttling effect of the intake air shutter valve or increasing the passage area during cold period of the engine, while braking effect of an exhaust brake is maintained also by reducing throttling effect of the shutter valve or increasing the passage area.