I have zafira 2.0 dti 2003 model, has been driving ok, and then the other day when i tried to start it, it just wouldn't start, juddering for about half min and black smoke coming out, then stalls. I had a look in the engine, just tried to push plugs etc. There was a round circular valve at the front of the engine behind the radiator, with a lever, i pullled it and started ok after that. does anyone what this is, is it an EGR valve? i have looked at other threads on the forum and it doesn't look like the pictures i've seen. can this be repaired and how? thanks.