Low idle while coming to complete stop?

Replaced injector o rings, super deep cleaned throttled body and IAC, OEM IAC and NEW TPS... no change. ran bk22 through. One time idled super low coming to a stop, into the 500s, wouldn't recover until I hit the gas. since then, idle at stop drops to 690 and then recovers. then vacillates between 720-750.

Assuming the issue is with the transmission or the engine at this point and will be doing compression this weekend.
 
Sounds silly, but I had same once.
Ended up being loose battery terminal!
Ran fine under load!
Died in the bum at idol.
Clean and see what happens.
 
Well my vacuum at the manifold is fluctuating pretty good. I don't have any reason to think the gauge is broken but I borrowed it from a friend who had never used it.

https://youtu.be/gnb12BEDUfI

Low and erratic, web search seems to diagnose valve springs. I will try to get ahold of another gauge to do a dummy check.

hottest (#6) plug looks like/there is a bit of oil on the first threads. these have about 4k miles on them.

https://youtu.be/K5qyzRsDhlc
 
Fuel pressure is a perfect 49

another view of a plug with what looks like oil on the threads. it does read as oil on paper towel. I don't seem to be visibly burning any or missing much oil from the crankcase, not sure if this is from a previous leaking valve cover or what.

AKs63Eh.png
 
In edition to the rapid fluctuation on the vacuum needle I'm noticing a good amount of exhaust pulsation and some spray out of the tailpipe but no smoke.
 
MickeyS said:
Well my vacuum at the manifold is fluctuating pretty good. I don't have any reason to think the gauge is broken but I borrowed it from a friend who had never used it.

https://youtu.be/gnb12BEDUfI

Low and erratic, web search seems to diagnose valve springs. I will try to get ahold of another gauge to do a dummy check.
Click to expand...


The bouncing needle is perfectly normal. Some gauges have a small valve to dampen the oscillations of the needle. The amount of vacuum at idle doesn't seem that low to me.
 
MickeyS said:
Fuel pressure is a perfect 49

another view of a plug with what looks like oil on the threads. it does read as oil on paper towel. I don't seem to be visibly burning any or missing much oil from the crankcase, not sure if this is from a previous leaking valve cover or what.

AKs63Eh.png
Click to expand...

lawsoncl said:
The bouncing needle is perfectly normal. Some gauges have a small valve to dampen the oscillations of the needle. The amount of vacuum at idle doesn't seem that low to me.
Click to expand...

thanks. if so, that's great news. everything I'm reading on youtube university and academy of google says this is abnormal, to not have a solid needle.
 
MickeyS said:
https://www.youtube.com/watch?v=vh3Z-F6KGkI

I watched this video and the wobbling needle on the gauge later still looks a lot better than mine.
Click to expand...

In the video, he's using a gauge meant for checking engine vacuum that has some dampening. The dampening is typically added by a restricted line, a weighted needle, or oil in the gauge. You're using the gauge on a mity vac hand pump which has no dampening so you're going to see the pulsing more pronounced at idle as each cylinder pulls on the intake stroke. If the needle is consistently dropping a lot once per rev rather than bouncing around at 6x the revs, then I'd suspect maybe a problem with one cylinder and then do a compression test which would be much more revealing. Even slowed down to 1/4-speed, I don't see more the needle wagging more than a few psi.

The gauge set I use to sync motorcycle carbs measures each cylinder separately and you can really see the oscillations on each piston stroke. This gauge set has valves on the vacuum line you choke down to get a reading steady enough to balance the carbs.
 
lawsoncl said:
In the video, he's using a gauge meant for checking engine vacuum that has some dampening. The dampening is typically added by a restricted line, a weighted needle, or oil in the gauge. You're using the gauge on a mity vac hand pump which has no dampening so you're going to see the pulsing more pronounced at idle as each cylinder pulls on the intake stroke. If the needle is consistently dropping a lot once per rev rather than bouncing around at 6x the revs, then I'd suspect maybe a problem with one cylinder and then do a compression test which would be much more revealing. Even slowed down to 1/4-speed, I don't see more the needle wagging more than a few psi.

The gauge set I use to sync motorcycle carbs measures each cylinder separately and you can really see the oscillations on each piston stroke. This gauge set has valves on the vacuum line you choke down to get a reading steady enough to balance the carbs.
Click to expand...

thanks for taking me to school. I'm going to get a stand alone vacuum gauge from HF to do a dummy test, then get a buddy to help me with the compression test soon. Will also spray around cylinders at manifold (again) as mentioned above, but I had done this a while back.
 
Lawson was totally right. Threw a HF vacuum gauge on the manifold and pull a solid 18 in hg at hot idle with the gauge only instrument. I passed smog today which is good news, if I didn't pass I was going to stop throwing time and money at the issue but the jeep passed with colors, so with perfectly strong vacuum and clean emissions I can start doing more work to get to the bottom of this.
 
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