In this paper an analysis of irrepeatability of cylinder pressure signal in static conditions of engine work was performed. Large irregularity of analysed signal was stated that follows the irregularity of engine speed and pressure value distortions in each quasi–period. A stationarity of cylinder pressure was studied. Resampling data method in the revolution angle domain was suggested. Due to this synchronised averaging, transformed signal was an effective method of eliminating distortions in the basic periodical signal. Static properties of signal deviations (deviations of cylinder pressure from pressure averaged in quasi–periods) were studied. It was stated that the analysed distortions are a wide–range noise and there is no reason to formulate a hypothesis regarding the analysed signal conformity with a normal distribution.