Abstract: The invention concerns a fastener driving tool comprising a tank for storage of a fuel, in particular liquefied gas, a combustion chamber connected to the tank, a piston that is movable in a cylinder for driving a driving ram, and at least one exhaust gas opening for ejection of exhaust gases after an ignition of a fuel/air mixture, where the development of the gas pressure of the combustion chamber is selectably reducible compared to a maximum pressure development, in order to affect a driving energy of the piston through the ejection, where, if a driving energy is reduced, the maximum pressure development after the ignition is applied over a first segment of travel of the piston.