When i first bought the car and used it some days it worked very good and properly. After a cold winternight parked outside, the morning after when i should start it, the engine started but the idle was very up and down. When giving throttle it idles up but leaves exhaustbangs and engine runs with idle up and down in rpm. I have demounted the EGR valve and it looks like the vacuum there works properly to me. ? Now the engine sometimes stops and sounds as missing some ignition.