Hi guys, i have just bought a 2004 Focus TDCI with 75000 miles on the clock. It has been running fine for the first 50 miles. I put some diesel in it earlier and after about a mile i pulled away from a roundabout and the car had little power and was blowing black smoke out of the back. This lasted about 10 secs then went back to normal. I left it for about an hour and took the car for a drive round the block and it did the same again for a short time then went back to normal. Any suggestions would be greatly appreciated. Many thanks