I bought this truck used and within 6 months i have had to replace the U- joint on the drivetrain, the entire braking system, heater core and the heat has also stop working and the dealership has no idea why.
Fun to drive around, small turning radius.
easier replacement of parts cost 1000 to replace heater core, better antirusting coating on the frame
I know this is 3 y/o.
If you still have your ranger (or for anyone else), as far as you heat not working, check your blend door actuator.
If it went out, it won't open the blend door.
It is a $20.00 part, that sits behind the glove box on top of the chamber that holds the heater core.
It will take some time, because it's in a small space, but if you get a flat wrench, and have lots of patience, it only has 3 bolts holding it in.
Remove it, turn on heat adjust thermostat, and if it doesn't move.....that's the prob.
If it does turn, it could be a broken blend door.
As far as the high rpm's, mines did that in neutral (5 spd man).
It was my TPS sensor had one of the wires kinked.
I straightened out the wire, and no more probs.
Ford actually has a recall on the wiring harness because it's too short.
I'm not a mechanic....just a guy who uses google and Haynes, who likes to do minor stuff on cars myself.
I forgot to mention, the actuator just plugs to a piece that looks like a phone jack. I think the dealer will charge a hefty sum to replace the actuator.
They remove the chamber and charge you the same as replacing the heater core.
Hope this helps.