The main concern is clunking going into drive
or reverse. I just replaced the u-joints and transmission
mount and it makes little if any difference. For a little history I took it in to the shop for a leaking brake line and when they backed it out they lost reverse. They put in a rebuilt transmission, This was about 2 years ago. I bought this Ranger new. It has about 167,000 miles on it. The tranny has about 5000. What else would cause the clunking? I already made the mistake of replacing most of the sensors. I thought I should try to rule out the high idle but it doesn't
seem high enough to account for the clunk. I followed the instructions to check the IAC:
1. connected Bosch 7677 for tach function
Start- 2000 RPM
10 sec 1500
35 sec 1200
1:10 1000
2:20 870-920
2. warmed up
3. disconnect IAC after warm up 870 steady
4. plugged in 1400
5. 30 sec 1030
6. blip throttle 1500 right back down to 1000
7. I couldn't find a Motorcraft or Hitachi IAC for a 2.5
I think it would run very smooth if I could. TIA.

 

RonD's info about the IAC says if you unplug it should either drop to 500 or die, not hold steady at 870. I'll post what I find.

another thing it has a junk yard throttle body off ebay because I took the original off and took it apart to clean it and was afraid I effed it up.

 

Hitachi IAC for 1999 Ford Ranger 2.5L

Bad link, screen shot below.
https://www.ebay.com/sch/i.html?_fro...+IAC&_osacat=0

 

Remember, an increased idle can also be a symptom of a vacuum or exhaust leak. I got the 3.0 replaced in my 00 Ranger at 250k. It had a fast idle and I couldn't get it figured out for the life of me. Even replaced the IAC.. Then I found a couple of the exhaust manifold bolts on the pass side backed out a few turns, on a new reman engine... I tightened them up and after several minutes of driving. The idle settled down to about 750 rpm's. The engine was seeing too much oxygen in the exhaust, so it was adding fuel and somehow it was increasing my idle instead of just running rich...

You should have your engine mounts checked as well. That can cause clunking when being put in gear. If your trans mount was bad, I would almost bet the engine mounts are too.

 

Thanks I'll check the bolts and the mounts. I'm using propane to check for vacuum leaks. I saw a small flutter on the multimeter/tach a couple places one was by the MAF and the other by the IAC. I'm still checking but I was wondering if I should use gasket shellac to get a better seal. Also 750 rpm idle would be nice. When I unplugged the IAC it must have triggered the CEL and it took a while to figure it out. Anyway if I have a few little leaks it seems like that could be bad, I just haven't seen anything big yet. And I wonder if the multimeter is a bad idea for rpms.

A source for Hitachi IAC for a 2.5

 

I don't like shellac on gasket surfaces. The gasket should be a o-ring type seal. Easily replaced and low cost.

As for using a DMM for tach. If it has the function and it's hooked up correctly, I don't see a problem with it.

 

OK no glue, the DMM seems to work right.

also on the propane, I was using a little hose that didn't work very good so I made a little wand I haven't used yet but I should be able to
put the propane where I want it, I hope. Thanks

Edit: the new IAC should have the right gaskets.