I have a 1999 XK8. The restricted performance message comes up fairly often and the car runs very rough. It usually goes off after a short time. Some time the "check engine" light comes on shortly thereafter. Neither message stays on long enough to bring to the dealer. Does the "restricted performance" message have to be on in order to get the proper codes? Can the correct code be obtained with the "check engine" light on?

 

The codes, especially for engine and transmission faults, will be stored in the cars computer, until a number of driving cycles w/o incident occurs, in which, they often clear themselves. You'll find, that doesn't happen very often. 99% sure, they're still there and can be retrieved. Do you have a scanner? If not, local auto parts stores offer this service as a courtesy.

Also, I recommend a quick search of the forum (see the search link above) for 'restricted performance' and 'limp home' in the XK8 and XJ8-XJR forums (<- identical engine and symptoms) for a good number of threads and help related to that very topic. There's lots to go over, so get a pen and pad out and be prepared to take some notes.

all the best of luck!

 

...oh yah, I wouldn't be doing my job if I didn't welcome you and suggest an 'introduction' post in the NEW MEMBER area, for everyone else to say Hi.

 

My 2006 S-type 2.7D decides to go "restricted performance" quite at random. My scanner never shows any errorcodes, and a mechanic's pro-scanner didn't either. Since it happens only very occasionally, I've not bothered to seriously investigate. But I did find one thing. Getting in the car, starting up, seeing the yellow MIL light on, I revved the engine in neutral for abt. 10secs. at 3000rpm., switched off. Waited a few minutes, restarted -- MIL light gone! No restriction!
Hope this helps you...
Leedsman.