If the peripherals are OK (throttle body and pedal assembly), that would normally only leave two options.......wiring integrity (which can be a source of angst for many members' various faults) or the ECM.
I am loathed to suggest the ECM as it is expensive to replace and I don't want to be pointing the finger at it simply as a last resort.

I haven't seen Thermo pop up on this thread yet, and he might have some thoughts on some other tests or ancillary sources of your problem.
I'll reach out to him to see if he can possibly take a look over this thread and make any suggestions.

 

theskylark62, from what I have read (didn't read each and every post, but I have a good idea of what is going on), you have only 2 problems as I can see at this point. What I would say to try is to remove the intake so you can watch the butterfly valve. Now, have a second person depress the gas pedal to hold the throttle at some mid point (exact location is not critical here). Now, as you watch the butterfly valve, wiggle all the harnesses that you can. You want to specifically wiggle those running to the throttle body and to the ECU. If you see the butterfly valve move as you wiggle a harness, you have a broken/damaged wire in that harness. If wiggling the harnesses in the engine bay do not seem to do anything, then that leaves option 2 which is your ECU needs to be replaced because the drive circuit for the throttle body is faulty (most likely failing after a minute or so of driving due to getting too hot).

Part o fwhat is happening is once the computers see the throttle not respond to the pedal, it locks the throttlebody down so it will not cause uncommanded accelerations due to the failure. As a result, it forces the throttlebody closed and only will let the car idle at some preset speed. I am leaning more towards the ECU only because you are also getting oddball errors on the instrument cluster too.

 

Thank both of you very much. I just checked resistance between TPS and ECM, and both are fine, wiggling didn't change them. I will try the partial pedal test and wiggle the wires when I have an assistant available, but I'm afraid it's coming down to the ECM. will let you know. If it turns out to be ECM, are there many other models that might interchange? If any.

 

Also, if I find a deal on a used ECM, does it have to be "flashed" like some vehicles? Is there a relearning procedure? Thanks again for all you guys do for us.
Dan

 

https://www.jaguarforums.com/forum/x...ptions-194959/

 

Hello Dell, I read all the way through the post above, and have another question: I have 1 transponder key and 1 valet key (which didn't seem to work only time I tried), if I do have to get programming, can they do it with those, or do I have to get another transponder key?
Since valet key doesn't seem to work currently, is that any indication what might be causing my problems (above)? I bought this car with this problem, and am trying to straighten it out for my wife. I only tried the valet once and hurriedly, so I will check it again. Thanks, Dan.

 

Yes, as for a valet key I have no experience with those. Seems rather counterintuitive for an X to have a valet key, as other Jags use a hidden (glove box, etc.) Valet button that sets the mode. This prohibits entry into the trunk (no key entry on an X anyway) or the glovebox when locked with a standard key by a valet key. On our X's there is no valet button. Glove box entry (maybe?), but trunk is simply a button on the boot lid (or regular key fob).