The throttle plate on my 98 4.0 is not closing all the way (if I push it down, the idle drops 2-500 rpm) I cleaned the throttle body a little but not any different.
The plate also seems a little loose, as-in it moves side to side a good mm.

Could the throttle spring be going bad?
Or does it need a new throttle body?

pushing it down all the way makes it idle at 600 rpm, and it normaly idles hot at 800-900rpm. which is too high.

 

Have you unclipped the throttle cable to see if it closes then? If the throttle cable is not retracting fully when you release the accelerator pedal, that will cause the problem you have. If so, you need to replace the throttle cable.

 

I think the spring is the problem, that and the 205k miles

 

If the tiny set screw isn't set right, the steel blade wears a burr on the aluminum throttle body, holding it open a tad.
Take it off, file off the burr, set the set screw so it closes but does not quit touch.