Recirculation of exhaust gases has been developed as a method for inhibiting formation of oxides of nitrogen during the combustion process in an internal combustion engine. In general, it is desired to recirculate exhaust gases at a rate proportional to the rate of engine induction air flow. To accomplish that purpose, exhaust gas recirculation (EGR) control assemblies have included an exhaust gas recirculation control valve pintle positioned to maintain the pressure in the EGR passage upstream of the pintle equal to a reference pressure. Recirculation of exhaust gas has thus been varied with exhaust backpressure, which in turn varies as a function of induction air flow, to provide exhaust gas recirculation substantially proportional to induction air flow.
In order to control the pressure in the EGR passage, many such EGR control assemblies have a hollow valve stem sensing the pressure in the EGR passage through openings in the valve pintle and communicating that pressure to a transducer. The transducer causes movement of the valve pintle to the position necessary to achieve the desired pressure in the EGR passage. In some such EGR control assemblies, however, exhaust gas deposits may form in the hollow valve stem, thus impairing the response of the transducer to changes in pressure in the EGR passage.