Cadillac Repair: EKG Valve, 1989 cadillac fleetwood, exhaust gas recirculation valve

Question
My brother has a 1989 Cadillac Fleetwood that is having some problems. He was told to disconnect the EKG Valve, (I am not sure that is the right term. But it is behind the carb.), and let the car run. Upon doing this, the vehicle ran smoother. When reconnected, the vehicle started runnung rough. Question, exactly what is the valve's purpose.

Answer
Hi James, Maybe what you ment to say was EGR valve...exhaust gas recirculation valve. The purpose is to sent exhaust gas back into the intake manifold so any unburned gas can be reburned hopefully and the other thing it does is lower the combustion temperatures so that the engine doesn't produce NOx...knocks...which would cause you to fail your emmissions test and have a ping/knocking noise when accellerating. There are 2 reasons why the engine ran smoother with the vacuum line disconnected. One is that the egr valve spring is weak...this is common. The other is if you have an egr solinoid of some type then it might be leaking and allowing vacuum to the valve when its not supposed to. Further testing will need top be done to determine where the problem lies. Unfortunatly if you leave the vacuum hose off the egr valve then the computor will know this and turn on the service engine light and set an egr code so you will need to get this fixed. Hope that makes sence. Bill