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It is the function of the thermostat to regulate the temperature of the engine coolant. If the engine is not warming to the NORMAL temperature range, your thermostat is not closing sufficiently.
The engine coolant temperature (ECT) sensor is located in the coolant line below and aft of the throttle body.
Unlike earlier Fords, the EEC - IV electronics in a '93 Ford do not function by the temp. sensor sending a direct signal to a "switch" that turns on the fan.
The ECT sends a signal through the ECM that then sends a signal through the IRCM/CCRM (look up the abbrevs by doing a search here) that then controls the fan.
1. Stop driving the car now unless you are planning to replace the CAT convertors sometime soon.
2. Replace the thermostat ASAP, and do NOT install one that opens at any less than the proper temp.
That's where to start, anyway. I'm sure that others will fill in the blanks for you. The fan couldn't cool down the engine enough to cause black tailpipes if the thermostat is functional, I believe.
185 is OEM for a t-stat, but a 195 will work just fine. Make sure it has a jiggle valve in it. Buy Motorcraft if possible; stant, etc. do not have the correct jiggle valve.
If you can't fine one with a jiggle valve (it's basically a tiny little hole at the top that allows air bubbles to get through without letting much coolant through), just get a tiny drill bit and dill a wee little hole at the top of the t-stat.
Yes, the ECT sends a signal to turn on the fans when it gets to about 205, but if the thermostat is stuck open (as it VERY commonly does - mine has twice), the coolant will never get a chance to heat up correctly as it keeps going through the radiator instead of through the block again. If the coolant never gets hot enough, the fans will never turn on, and you'll run rich as s#*%.
But yes, definitely, replace your thermostat. You should be replacing it often... every time you do a coolant flush is optimal.