I've been through all the different threads on weird idle issues with the Rangers as far as I can tell.
Mine was the typical low rough idle at times, but would smooth out after sitting for a few seconds after stopping.
I replace the idle control valve and the plastic sensor on the throttle body, cleaned the throttle body of all the carbon build-up
and the idle was higher than it should be. I attached the battery cables to clear the computer settings twice to make sure that
wasn't the problem. Still, it idles way too high but settles down after a few seconds of stopping, Kind of opposite of what it did before
spending the hundred bucks on the two new components. (Idle air control valve and little plastic thing with the two phillips screws that are a pain to get out - the guy at advance auto told me I need to replace both)

I unplugged the new throttle control valve and now the idle seems normal.

Does that mean the new control valve is bad ?

 

I had this problem. If I reved the motor a little it would idle rough for a few minutes then return to normal. I had good compression, the engine controls all checked out. I finally pulled the head and found my valves were leaking slightly. They were not bad enough to lower the compression. A Valve job fixed it.

 

Makes sense. With 186,000 miles on my truck, I'm sure the valves and springs are not working 100%.

I can live with the rough running if I could get the idle to run at a somewhat normal RPM. I still have the new throttle control valve unplugged but on cold start ups it doesn't want to idle right away so I'd
like to figure this out before winter hits here in IL.