Ford Repair: Stalling, everyday occurance, coolant temp

Question
Clay, I own a 1992 Ford T-bird, V-8 5.0 with 117,000 miles. Every morning it takes about 7-10 min to warm up. If I don't wait this long the engine will stall when accelerated (in gear, of course). During this time (7-10 min) the temp gauge will rise from below "C" to about 3/4 the way up (driving or not) and then settle back down to a little less than 1/2 way. After this everything is fine. This also happens when I leave work around 5pm. I changed the thermostat around 2 mo ago and this problem WAS very rare but now it's an everyday occurance. ANY idea on what this could be?
Thank You very much for your time...

Answer
Michael, your temp gauge sounds like it is working properly - on a cold engine, the thermostat is closed to heat it up quickly, then the gauge drops back some as the thermostat opens to allow the cold coolant in the radiator to be introduced to the flow.
The stalling on a cold engine, though, is a concern.  Do yo get a 'check engine' light? If so, I'd have that diagnosed first as it will give a clue to what system is out-of-range.  Then, I would check the fuel pressure and be sure that it is 35 psi or so.  If a computer scan is available, see if the coolant temp sensor is accurate when cold, compared to another temp sensor such as IAT or MAT.  
Hope this helps... your Ford dealer should be best equipped to diagnose the stalling concern, but will need the car overnight to duplicate the conditions.
Clay