Why does my Fiesta stall while idling all the time?

sounds like a fuel problem could be a fuel pump or filter problem you would need to have that checked. other reason for stalling it could be a faulty idle, but with a faulty idle it should still start back up first time.. so would check spark plug leads and plugs. also check for air leaks, its common for the plastic air lines to crack replace with rubber type.

might just need a good tune

I recommend doing a leak down test. It could be valves or blow by. Also try cleaning the idle air control valve (IAC-V), the exhaust gas recirculation valve (EGR), and fast idle valve (if it has one).

This sounds like you have a bad idle sensor. Replace the idle sensor and it should solve the problem.

MOST OF THE TIME BEST TO LET DEALERSHIP REPROGRAM IDLE BECAUSE STALLING AND WAITING FOR CAR TO RELEARN TO IDLE.CAN BE DANGEROUS.FOR A CAR STALLING OUT AROUND MOVING TRAFFIC.

TPS throttle position sensor

Given your high guage temps of 210 degrees and high ambient temperature of 100 degrees, your engine's stalling can very likely be linked to either one of these three causes: 1) vapor lock; 2) percolation; or 3) PCV malfunction. Here's a really good diagnostic article that precisely addresses this issue of yours:
http://yourhandymanzone.com/Your_Handyman_Zone_How_To_Pages_Vehicle_Car_Zone_Cars_Trucks_Vans_Engine_System_Engine_Stalls_When_Hot.htm

Hope this helps! Brad

Hello;
First we need to ascertain the problem. When the vehicle stalls, does it start up immediately? Does it blow smoke out the exhaust on restart? Before it stalls, does it chug and sputter or act like you turned the key off? ALso, which engine and transmission have yoou in this truck?
Thanks;
Rich
RPM Northwest

On thing to check is the air duct hose that connects from the throttle body to the air cleaner housing. If it gets cracked it will cause stalling problems and very rough idle.