I've been having the same problems and found some information on another site that seems to answer all the questions and problems.
There's two TSB numbers associated with this problem (15431 and 15630).
15431 - LACK OF POWER IN HIGH AMBIENT TEMPERATURES
Some 1999-2002 Expedition and F-150 vehicles equipped with 5.4L 2V engine may exhibit a lack of power condition when the vehicle is operated in ambient temperatures above 100 degrees F, particularly during stop-and-go driving. By design, the PCM calibration retards the ignition timing to prevent detonation when the inlet air temperature (IAT) reaches temperatures above 140 degrees F. If the lack of power condition occurs only when the IAT is above 140 degrees F, do not replace parts in an attempt to service. Engineering has developed a new calibration which will be available early in the first quarter of 2002. If the condition exists in other temperature ranges, proceed with normal diagnostics.
15630 - LACKS POWER IN HIGH TEMPERATURES - REPROGRAM PCM
Some 2000-2002 Expeditions equipped with a 5.4L 2V engine may exhibit a lack of power condition when operated in ambient temperatures above 100 degrees F, particularly during stop-and-go driving. This may be due to PCM calibration, which retards the ignition timing to prevent detonation when the inlet air temperature (IAT) reaches above 140 degrees F. A new calibration is available to service this condition. If the condition occurs only when the IAT is above 140 degrees F, reprogram the PCM to the latest level via the just-in-time process if your WDS communicates w/Fordstar. Also obtain calibrations on the Ford Professional Technician Society (PTS) website - select 'WDS' then 'PCM reprogramming' and click 'Instructions' for downloading. Calibrations are scheduled to be included in WDS release B17.10.
The Ford dealer will update or flash your pcm for $115 and it takes an hour. Everyone at ford denied this computer issue until I found a Ford PCM tech who said Ford was avoiding a safety recall for the loss of power in an emergency situation.. Enjoy..
