It improves overall engine efficiency, resulting in a more stable idle, better fuel efficiency, and reduced oil pollution. EVAP Emisson Vapor Purge Valve Canister Solenoid For Chevrolet For Caprice. Vacuum solenoid valves control the amount of exhaust gas entering the intake manifold so that a certain amount of exhaust gas flows into the intake manifold for recirculation. The valve has strict control capability, which can adjust the turbo pressure in real time to ensure a good performance of the engine under different working conditions. The function of the EGR valve is to control the flow of recirculated exhaust gases depending on the engine load., Manufacturer: hmeng