4.0 Throttle shaft worn?(yes) Try this $3 fix. I did it yesterday
 

Tune issues? Don’t over look this.
This old boy posted this video, and I tried it out yesterday. He apparently has done quite a few and said ' I never seen one that didn’t have play in it'
What it does is moves where the little roller bearings ride on the throttle shaft, about 1/16 inch on both sides for a total 1/8" , and replace the 4 o ring seals. So it only gives 1/16" new surface to the bearings so I don't expect it would last as long as a new TB. But it does work great, and you can see the difference. Home Depot has the O rings for under $3. But they were out of stock so went to Harbor Freight like he said in the video. Remember there are 4 old O rings to take out. Like he said mine were brittle and not sealing. Whole thing took about 40 minutes once I had the O rings.
Definitely took the play out of the shaft, which will let the TPS read more correctly and it also wont rock around on your new O rings so no vacuum leaks. I can tell the difference .
Just remember when you're digging out the old seals there are 4 of them. Video didn't make that clear right away.

This vacuum leak is what causes idle surge, where the idle speed changes just slightly up and down. This happens because the PCM has to relearn how much air is passing thru the IAC every time the throttle plate closes and adjust the position of it to compensate. For those of you who are familiar with carburetors, worn throttle shafts cause different idle speeds when you ease the plate closed or you snap it closed. Holly carbs were the only ones I've seen with nylon bushings on the throttle shafts to help reduce this wear. The idea of roller bearings is fascinating! I had no idea these throttle bodies used them.

My WJ with 260K miles on it has a bad case of idle surge. Now I know it's cause. I also know why Seafoam destroyed my TPS! You could more than likely do the same by pushing the bearings in and putting both o-rings on the outside, making them easier to replace the next time. There will be a next time because o-rings don't like being used as rotary seals when run dry.

Great post, 97grand4.0! 012 o-rings. Good to know.

I defer to the guy in the video. As far as the O rings,... two things. First if the shaft is more stable, less wear on the O rings. Second, he says these O rings have nylon in them. Maybe,? I can say the installed ID is almost the shaft OD, very little drag. They should flatten out like the old seals.

Forgot to mention about the sizes. 012 is not the size, that’s the number harbor freight assigns to them in the kit,

They are 1/2" OD x 3/8" ID x 1/16". Home Depot was out, but sells 10 of them for $2. something. Ace had only 2 and they were $1.19 each so I passed those.

If you can disconnect your cables and grab hold of the shaft and wiggle it, it's bad.

Thank you for the info. HD's part number is 583970, I believe.

McMaster-Carr has Buna-N 012 0-rings for $2.82 for a package of 100.

97Grand4.0. Great post and GREAT video.
chasing down a different vac leak on my 01 WJ 4.0 today and found smoke billowing out of front throttle shaft. No idle issues, just another thing to Lois sleep over-hahahaha
im going to search for more heat resistant green(a/c) O rings

First I've seen of this issue. I recommend FKM (Viton) o-rings over buna-n because Viton has a much higher temperature rating. McMaster-Carr has two different FKM variants:

Standard FKM: https://www.mcmaster.com/9464K17/

Softer FKM: https://www.mcmaster.com/1284n113/

Both have the eact same indicated dimension for an 012 o-ring. Both are indicated to be suitable for dynamic sealing.

Thank you very very much. HF has a green O ring kit that I believe has a 1/2 X 3/8.
great and fast response👍🏿 Weekend project, so that I can now sleep at night.

Good thread to bump. This is an easy issue to overlook.

Anyone have a magic trick to getting the bearings out? Looks like they're pressed into blind holes. I found replacement bearings (with the nylon o-rings), but getting them out (nicely) looks impossible.

Bearing: SCE67-PP-L271/STD

One other source to high temp/green O rings
(1/2” X 3/8 x1/16) at the “O” Ring Store in WA state.
https://cimg2.ibsrv.net/gimg/www.che...446b9116c8.png

XJLimited- thanks!! Amazing contributors in this Forum. I too would like to know best approach to press out the bearing