I assume you aren't talking about your 2001 XLT?? There is also a thread in the 'Sticky' section, MFT Acting Up? that you may want to look at. Other than that you can try a Master Reset which will mean re-entering some save info or a negative battery cable disconnect for a short time which will mean the transmission will have to relearn its shift points and the idle and trim fuel settings have to be relearned. There is an explanation on how to do the latter in your Owner's Guide if you want it done right away.
Peter