Clogwork_orange

Greetings I have only recently become the owner of a 2010 Subaru Forester Diesel (115,000 miles). It is a bit of a Jekyll and Hyde. On cold mornings the car would run rough for a couple of miles and make a loud clattering noise when accelerating. The clattering seemed to be worst in the 1500 -1700 rpm range and would disappear when I came off the accelerator. As soon as the heating/airco kicked in (after 1~2 miles), the roughness would subside and the clattering would be less noticeable; once the blue engine cold light extinguished, the engine would run smoothly and the clattering would either disappear or be barely noticeable. Under warranty the garage has replaced the glow plugs and cleaned the air system. Plus quite a bit of fuel system cleaner has gone through. The rough running has more or less disappeared and the clattering is a lot less. I drove it on 200-miles round trip (motorway) and it was sweet; however, the clattering has not gone altogether. When clattering, the belt tensioner moves about, but I think this is a symptom rather than the cause. Somehow I have the suspicion that the injector/ECU timing is wrong when cold and readjusts when warm. Despite its foibles I still like the car though…