The article concerns the possibilities of use of the method being able to assess of the combustion process and its lack in internal combustion engines of railway traction vehicles, that bases on the use of vibration signal parameters. The paper includes the results of research conducted on the engine test bench with a single cylinder research and compression-ignition engine with direct injection, and tests for the engine of a diesel locomotive in the exploitation condition. Possibility of the vibration signal estimators application to the assessment of a combustion process lack in an internal combustion engine and a high reliability of combustion process diagnostics basing on the above method have been proved.