3.0L V6, Automatic transmission, 172,000 miles.
My Tribute recently develop a high idle problem if the AC is on when coming to a stop. Driving down the highway at 2,000 RPM+, the 3.0L engine remains at 2,000 RPM requiring extra force on the brake on the brake pedal. At a complete stop, it will fall back to a normal idle speed after a few seconds.
I do not want to just throw parts at it hoping to hit it at some point. My thoughts would be a vacuum leak or the sensor that raises to engine speed when load is applied. I checked the throttle cable and it is not sticking so that rules out that one part.
The vehicle is all new to me bought just a few months ag.

 

Not sure if you’ve already gotten this fixed, but I had the same issue with this year of Tribute. I would come to a complete stop at a stoplight and it would still idle at 2000-2500 RMP. After a couple seconds it stopped and would fall back to normal idle. It would occasionally even stall on me. Eventually found out it was the alternator trying to keep the battery charged while running at a stop. Replaced the alternator and it ran like a top ever since.