Abstract: In an oxygen sensing unit, an oxygen sensing cell with a closed outer end is encircled by a side wall of a protective shell or shield, and recessed from an open mouth of the shell. The cell and shell are mounted in a plug made up of a closure cap with an externally threaded section and a plug body with an internally threaded section complementary to the externally threaded section of the closure cap, the two parts of the plug cooperating to hold and compress the shell and cell, mediately or immediately, and permit the removal and replacement of the cell.

Abstract: An exhaust gas recirculation (EGR) valve for controlling the amount of exhaust entering the intake manifold of an internal combustion engine. The EGR valve comprises a universal base so that a single base may fit many makes and models of vehicles, a diaphragm valve having two ports facing opposite directions protruding from the top of said valve, making connection of a vacuum hose to the EGR valve easier, and a back pressure transducer wherein the transducer has means to alter the vacuum required to close the valve.