Hi,
I had this exact situation on my 99 XKR. The reason was the Lambda sensors
as found at the emissions test (MOT in the UK), the engine still performs OK
as the computer compensates. I believe there are 4 sensors, in my case only
the Jag dealer could detect the one that has failed not the test centre.
In my case this occurred after the car stalled during a journey, I switched
off and restarted and haven't had the problem since. The dealer changed the
throttle body at the same time because of the stall as this was the reason
for an early recall on this model. It was done for free possibly as I've
always had the vehicle serviced by the dealer.
Best of luck.
Howard
"KarinXK8" <karinwacaser.RemoveThis@yahoo.com> wrote in message
news:1181838270.503248.35420@i38g2000prf.googlegroups.com...
> Does anyone have any suggestions for what I should do: over the last
> couple of months, my average mile per gallon has fallen from 18.5 to
> 16.4. What could be causing this?
> >> Stay informed about: 99 XK8 gas mileage going down