I have a 91 ranger 2.3 automatic 2wd, I have had her for about a year with this same problem, I replaced the IAC, TPS, plugs, wires, fuel filter, air filter, cleaned the intake/etc, checked for leakes intake manifold, hoses. and reset idle to specs. The problem is that the Idle,( even on a warm engine), will take a minute or two to come down to 700 rpms, after kicking it down, even if I just shut it down for 15 minutes. if the idle is not at 700 or less rpms, when I put her in gear,( forward or reverse) the idle will rev up and it will slam into gear. I was told by a trans shop a while back that it could be a valve in the trans thats leaking and pressures not building fast enough, and thats why it revs and slams into gear. Anyone have any ideas!!!

 

check your vac lines that go to the manifold for trans fluid at the (manifold or vac tree)
If you have trans fluid in these lines than your trans modulator valve is bad. (Check engine oil for trans fluid too) I had this happen to a 94' ranger.

 

I forgot to mention that I had replaced the modulator and at that time (about 6months ago) there was no fluid in the hose. However, There is no EGR valve, or EGR position sensor,(not to be mistaken for the TPS). There is no cover plate to be found where the EGR might be located. I read once somewhere online that some 91 rangers with a 2.3 eng did not come with one? However if someone had removed the EGR, could they have routed the hoses wrong. there are no loose hoses and they are all going to the intake tree. The idle issue is not normal, even if the engine is all warmed and in the summer, I have to kick it down and wait about a minute for the idle to creep down, everytime I start it. Any Idea's will really help. thanks.