natty

After going rounds with my truck and checking most of the things I've researched (on here mostly), I took it to the dealer. They checked everything and after cleaning and adjusting the idle screw, it seemed to run good. Soon after driving it though, the low idle came back (although it no longer stalls). I have adjusted the idle screw 4 or 5 times now (just doing it by ear). Unbelievably, soon after, the idle always goes back down.

Now I haven't done a clinical test yet with marks and photos and such, but I could swear the idle screw is creeping back down. Is this possible? Maybe the hole loosens up when it gets hot and allows the screw to rotate in? The threads don't seem to be sticking up enough for me to have progressively adjusted it out 4 or 5 times.

So does anyone have suggestions on how to lock the idle screw so I can eliminate creep as the problem? Should I just use a little low-strength thread lock?

Inferno451

I guess it's possible, but unlikely that that's happening. I know there's no way mine would do that. You could always put some plumbers tape on the threads, that would make sure there's no vacuum leak and keep it in place. I'd still be checking for vacuum leaks, personally.

natty

Either it's creeping back in or, after backing it out five times, some other system in the truck is lowering the idle back down every time---with the idle screw getting more and more open each time. That sounds even less likely.

Also, one time after it was warm, I could turn it with my thumbnail

I was thinking of teflon tape too, so I'll try that.


I really really hate to think that I went through all of that hell with the TPC when it was something this basic.

Bad Karma

My truck ('91 22RE) was/is doing the same thing. I did trace it to the idle screw, the o-ring was shot and it allowed the screw to spin in either direction with engine vibration. The last time I found the screw spun all the way out! I installed a new o-ring and used some teflon tape on the threads.

That fixed it for several months, but just a few days ago, my idle dropped a couple hundred RPM again. I adjusted the screw back out, and that seemed to help for a while, but it still fluctuates sometimes. Haven't looked at it yet, but it seems like the screw is moving slightly again. I may try a bigger o-ring and see if that helps.

I have an extra throttle body, I also may investigate the possibility of installing a set screw or safety wire to hold the idle position...

natty

Update: It IS CREEPING. Easy to tell because when I went to screw it down to check how high it was---it was bottomed out. The o-ring no longer looks to be round in the cross-section due to it shrinking/being flat. It must have suddenly broke loose and after that, the friction of the o-ring was gone. So I'm trying teflon tape just at the top where the o-ring is while I research (or go buy an o-ring assortment from Harbor Freight).

Didn't see an o-ring for that in the parts schematic. I guess I'll just have to do trial and error to find a replacement. Does anyone happen to have the spec on that o-ring?

Bad Karma

I used an o-ring from an assortment kit, whatever fit. I also used the teflon tape. I may try to find a better o-ring sometime, though.

ShadowTek

I didn't even have to use a thumbnail on mine, I could just grab the sides of the screw between two fingers and adjust it the half dozen turns or so it took to get the RPMs back down to 750. Needless to say, I don't expect it to stay there with it this loose.
At least I know what the problem is now.

natty

Glad this thread helped! For the record, my "fix" is still holding strong five years later, so I had no need to do any other mods

ShadowTek

Good to know that teflon tape can be a long-term fix.

I read in another thread that the exact metric spec for the o-ring is some Japanese standard that just happens to be in the Harbor Freight o-ring kit, which I already have. I think it's the biggest one on the smallest row (top-right), or thereabouts. They also say that it's the exact same o-ring for the fuel injectors, so it's good to know that I already have a stack of them ready to go.

Grego92

iTrader: (4)

Page 18 of my build thread if it doesn't take you right there. https://www.yotatech.com/forums/f199...4/index18.html

ShadowTek

Put the new HF o-ring in and the idle screw is a bit more snug now.
Thanks