An installation, insulation displacement, and terminating power tool, for inserting electrical wires into, and for electrically connecting the electrical wires to electrical contact members disposed within, an electrical connector, comprises a piston-cylinder driving assembly for inserting the electrical wires into the electrical connector. More particularly, the piston-cylinder driving assembly comprises a three-chamber pneumatic piston-cylinder driving assembly for developing an enhanced level of driving force necessary for inserting the electrical wires into the electrical connector.