1990 GMC C3500 EGR Vacuum Control Solenoid Replacement Cost

The exhaust gas recirculation (EGR) vacuum control solenoid is very aptly named in that it controls the EGR valve with engine vacuum. For EGR valve to help degrease harmful emissions, it opens up to allow exhaust gas from the engine to go back through the intake manifold to be reburned. This prevents unburned fuel and harmful contaminants from reaching the atmosphere. This valve cannot stay open all the time, so it needs a component to open and close it when needed. This component is called the EGR vacuum control solenoid.

When the engine control module (ECM) wants the EGR valve to open or close, it will either energize or ground the solenoid so that it opens or closes. When the solenoid is either opened or closed, vacuum will be allowed to flow, but the other position will block the flow of vacuum. Depending on the vehicle, when vacuum is allowed to flow, it will actuate the EGR valve, allowing exhaust gases to pass through the EGR valve and into the intake manifold.

As with any EGR issue, the most common symptoms noticed when the EGR vacuum control solenoid fails are rough idling, hesitation accelerating from a stop, lack of engine power, misfires, and, of course, illumination of the dreaded check engine light. If failure occurs with the EGR valve stuck open, the vehicle will suffer reduced gas mileage and decreased catalytic converter operations, not to mention the check engine light. Hesitation from a stop may also be accompanied by stalling or very low engine speed when slowing the vehicle down, especially from highway speeds. The vehicle may also hesitate for a short or extended time, then accelerate quickly as if the accelerator pedal were pressed to the floor.