Combustion engines operate over a wide range of power and speed. To the greatest extent, this applies to automotive and tractor engines and diesel engines operating at fractional and idle loads for a significant part of the operating time. When designing engines, the choice of their main design and layout parameters is carried out in a comprehensive manner, taking into account the provision of the required power and efficiency in the modes of maximum torque and rated power. However, ensuring the economical operation of modern highly accelerated diesel engines at low loads and idling causes a whole range of problems related mainly to the organization of effective mixture formation and fuel burnout, as well as to ensuring stable fuel supply. Thus, the cycle dose of injected fuel in idle mode is 8–12 times less than the cycle dose in nominal mode, which determines increased requirements for fuel equipment and difficulties in ensuring high-quality mixture formation. At the same time, diesel engines operate in idle mode up to 50 % of the total operating time, consuming up to 15–20% of the fuel. For truck engines, the relative idle time is approximately 20–25 %. Thus, the development of measures to improve the efficiency of diesel engines at idle is relevant. The purpose is to perform a numerical analysis of the effect of switching off cycles in diesel engines for autotractor and diesel locomotive purposes on the working processes in the cylinder and the indicator parameters of the cycle in idle modes. When writing the article, traditional methods (comparison, description, and measurement), generallogical methods and research techniques (analysis, generalization, etc.) were used. A numerical analysis of the operating cycle of a diesel engine equipped with a cycle shutdown system was performed. The relationship between changes in fuel injection characteristics when cycles are turned off with indicator indicators of the engine operating cycle in idle load modes is disclosed. It has been established that the expediency of switching off cycles in a specific engine operation mode is determined primarily by the features of the injection, carburetion and fuel burnout processes.