Fastener-driving tool with one or more combustion chambers and an exhaust gas recirculation system

A method of operating a fastener-driving tool including a housing, a combustion chamber in the housing, a cylinder in the housing, a piston chamber in the cylinder, a piston in the piston chamber and movable relative to the cylinder from a pre-firing position to a firing position and back to the pre-firing position, and a driver blade attached to the piston, said method comprising:

• communicating a first portion of exhaust gases out of the combustion chamber and to atmosphere via an exhaust conduit;
• communicating a second portion of the exhaust gases out of the combustion chamber and then back to the combustion chamber;
• communicating a third portion of the exhaust gases out of the combustion chamber and then to the piston chamber to assist in returning the piston back to the pre-firing position;
• and
• controlling the communication of the first portion of exhaust gases, the communication of the second portion of the exhaust gases, and the communication of the third portion of the exhaust gases via an exhaust gas recirculation valve in the housing.