While cruising in my Focus CC there was sudden loss of power that lasted for aprox 5-8 seconds. I depressed the clutch to see if it would idle, and it did, and when releasing the clutch again, everything worked normal again. Something similar happend one week ago, I was driving around constant speed then suddenly starts jerking. It lasts about 10 seconds, then everything goes back to normal. What can be the reason for this? Air in the fuellines? A few days before this happend I almost ran out of diesel (felt it judder once), but managed to get to the station before it stopped.