hi all,

I have this strange problem with my year 2000 xjr:
When the fuel tank is full I have "restricted performance" and if I try to drive harder the car sort of "hiccups". When I'm not asking for too much power it runs smoothly. The idle revs are fine, calm. All cylinders firing.

As the fuel tank empties a bit the "restricted performance" goes of for moments. And if the tank gets emptier it appears rarely, with tank bellow 2/3rds it doesn't appear anymore even when I drive it flat out.

I went to a workshop to have the error codes read out, but right in that moment the "restricted performance" went away and there were no error codes in the system.

any ideas? fuel pump? some tube/breather plugged?
many thanks.