about a jag xjr (x300)?

[Lee]

i used to have an x308 v8 xjr if you left it in second and got to the red line it would jump about as the supercharger cut in and out well i recently bought a x300 xjr and if you put the pedal hard to the floor as you accelate from standing the car does the samething it jumps back and forth and does accelarate any ideas?

[Timbo is here]

The first car was "bouncing" off the rev limiter (electronic over rev protector)
The second one seems to be misfiring and there can be many causes for that.

[bracken46]

The above answerer is right, it's hitting the rev limiter so you don't screw up the engine any worse than you all ready have. I really, really hope you've got a x300 XJR with a manual box, if not I'll be looking forward to you paying through the nose for the transmission damage you're wreaking. Keep in mind those superchargers are more delicate than the one fitted to the 308 cars, and you're in for a world of hurt if you abuse it.