A purge valve is a device used in a vehicles evaporative emission control system to remove excess fuel vapor. It is also known as the canister purge valve and is a vital part of the EVAP system that seals the fuel system of a vehicle to prevent harmful fuel vapors from entering the environment. The valve traps the fuel vapors created in the fuel tank and prevents them from escaping into the air. The valve operates using a solenoid, which can sometimes malfunction and cause it to become stuck open or closed. Symptoms of a failing purge valve include poor fuel economy, engine power loss, and the check engine light turning on. The process of fixing or cleaning a purge valve is not complicated and should not take more than a couple of hours.