Thermostat or something more

I do not think this is thermostat , in city driving if it was thermostat the issue would be worse , if you have something clogging the radiator fins , mud , leaves etc... this could cause an overheat

P1112 Engine Coolant Temperature Radiator Outlet Sensor High Inpu

If you have a viscous fan hub then have it replaced as it is not drawing air through the radiator at idle or slow speed (crawling traffic). Check that are no air locks in the system as they will cause heating problems.

It could be the thermostat but you need to check the fluid level and for any leaks (these could even be pin hole) first. If you have one of those infra-red temperature gauges you can check the temperature of the cooling system in the engine bay to double check. Generally the engine temperature should not go much about 90 deg C - this is when the electric cooling fans kick in - are these turning on?

Before even trying a new thermostat, try blocking air flow past the radiator and engine area with some cardboard in front of the radiator. If your temp. gauge shows below half all the time, try a hotter rated thermostat, one that stays closed just a bit longer. Say your t-stat is rated at 190 degrees, get one that is rated at 193 degrees- do small raises to avoid overheating-and in the summer, you may want to go back to the lower rated t-stat.. A parts store or Ford dealer could help you pick an optional thermostat.
To replace, drain enough coolant from the radiator so the level in the engine is below the thermostat housing. Take off the upper radiator hose from the thermostat housing. remove retaining bolts or nuts from the housing, any other obstructions, and pull the housing off, replace thermostat, clean the gasket mating area on the housing and the engine block, use a new gasket and fit all back together. Careful not to overtighten the t-stat housing bolts: the torque specs would be small-about 15-20 foot pounds of torque-just snug them down good-you can always go back and re-tighten a little if you see a leak. So, all back together, refill coolant and overflow tank, run engine with radiator cap off till engine is hot, and thermostat opens-this will helpyou bleed air out of the system. When thermostat opens, coolant level should drop a little. Shut off the engine, top up radiator and overflow tank as necessary, and replace radiator cap. Check for leaks.

You know most people think of the worst when it comes to these things. Try this, let your run for about ten minutes then shut it off. Feel both upper and lower hoses and see if they feel about the same in temp. If not than it could be your thermostat. If everything feels fine then you may have a bad sensor.

if the temp guage is going high when engine is cold its the cable attached to the temp sensor touching the body at some point

if the engine is hot see if the radiator fan starts running if not see the cables that are attached to the fan and also see the thermostat

check the rad hoses for softness, my guess is the lower hose is collasping under high flow

check sensor
check actual temp with non-contact thermometer

follow the top radiator hose to the engine and that is where you will find the thermostate housing. drain the coolant completely then pul the housing off. make sure when you put in the new thermostat that you put it in that same way and direction the old one was. clean and dry housing before installing gasket and putting back to gether. refill the cooling system, and run with cap off for 30 min topping of the fluid as needed. run for 15 minutes with cap on making sure to keep an eye on the cars temp gauge. after done drive the car for at least 15 miles let it cool down and ceck the coolant level.

hope this helped
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