1994 Other Mercedes Benz Models runing very eratic on idle

hi i wonder if anyone can help i am curently runing a 220cdi elegance on start up it wont idle properly runs very eratic its as if only runing on three cylinders once you get up to 60 or 70 mph it runs smooth someone did sugest air mass sensor but not sure dont want to spend hundreds trying dianogistics if anyone has had simulare probs woulde like to hear or if you can help would appreciate email