One problem related to power train has been reported for the 2004 Jaguar XJ8. The most recently reported issues are listed below.
Well I was driving along and all of a sudden just lost fuel power, so I pull over, cut the car off, and started the car up again and drove about a 100 yards and it repeated the same thing over again. I must have did it at least 6 times till I got home. So I'm thinking that it might be the throttle box, it's a fuel and electrical problem.