85-91 EGR Control Valve Relay Solenoid

The EGR (exhaust gas recirculation) reintroduces spent exhaust gases back into the combustion chamber to reduce oxides of nitrogen. The EGR valve on 1985-1990 Corvettes is opened and closed by the EGR Control Valve Relay Solenoid. This part is also commonly referred to as the EGR Relay, EGR Solenoid and EGR Switch. The solenoid fails at a much higher rate than the EGR valve and typically causes your C4 Corvette to stall, experience rough idle, engine knock and surging or hesitation during acceleration. Before replacing the solenoid be sure and remove the EGR valve and make sure there are no carbon deposits on the valve itself. If it is clean or if you clean off the deposits then it is generally safe to assume your Corvette's problem is the EGR solenoid.