exasemech

Another random thought:

You cleaned the tb
The tb has seals on the throttle plate shaft
Those seals wear
Crud builds up in the throttle body.
crud could be sorta sealing up worn seals
You removed crud so now leaks past shaft?

Spraying stuff where shaft comes through tb would be check

cruiser54

Gasket leaking? I wish I had thought about spraying it..........

arpunk

Got a new IAC for test purposes from Duralast (hooray, China!) and the high(ish) idle persists. Interestingly, the o-ring it came with is too big. Original o-ring is perfectly fine and sealing tight so I reused it and can rule out the IAC. I'll probably return it.
Took off throttle body and gave it a good inspection. Mating surfaces on intake manifold and throttle body are both clean, gasket is good, torqued down to 7.5ft-lb.
I know that I have externally leaky fuel injectors if I give them a little wiggle so I'm going to swap them out tomorrow hopefully. Maybe there is a slight vacuum leak at the manifold due to the old o-rings. Also waiting on the MAP sensor vacuum lines and elbows although in my experience a MAP vacuum leak results in horrible low idle, not high idle.
If the new injectors don't solve the issue I'll see if I can find a shop that can test my RPMs to see if the tach is off a little.

If I attach a video, do any of you think you would be able to hear if the engine is idling high (1k)?

Once I figure out the issue I'll post it so that the next person searching can hopefully get some tips that they may have overlooked.

74Plb

My 90 4.0 auto XJ idles at 1000 in park or neutral. In gear it idles at 750 or thereabouts.
i would personally call it good unless you have a racing idle. I chased a high idle for awhile myself it can be irritating to correct to say the least!
74Plb

arpunk

@74Plb Interesting… you’d think that somewhere in the FSM they would list correct idle speed or at least a range. Underhood sticker doesn’t list it either.

It feels fine at idle but it’s higher than it used to be and 1k seems high based on my experience with other cars.

I’m think either:
A) tach is incorrect, idle used to be too low, cleaning throttle body and IAC brought idle to where it should be but since the tach is incorrect, it reads high
B) idle is too high and needs to be corrected
C) tach is correct and idle is correct

Out of all the possible problems, this is minimal and the Jeep runs great otherwise so I’m not too stressed about it.

74Plb

My idle drove me nuts. I cleaned everything up like you have and it got incrementally better.
Someone in the vehicles past had tried to increase the idle speed by messing with the butterflies and cracked them open with the set screw. I bought my 90 as a Covid project and have just about everything sorted out.
Have any photos?
74Plb

The turbines are my latest addition
Hours of scrubbing to clean these up.

arpunk

I have those same rims! Everyone loves them but to me they don’t seem all that special. I’m not disappointed with them I’m just not over the moon about them.

I looked up my paint code: Black Cherry Pearl Metallic. It was repainted before I got it but based on my floor pans it’s a pretty spot-on color match. They could have done a better job but I’m happy.

How many miles on yours?

arpunk

@74Plb you also have the fender flares painted. Is yours a Laredo? I wonder if that was part of the trim package. You also don’t have the molding between the front and rear wheels on the lower part of the body. Maybe that’s a later year thing. I prefer painted flares and no body pieces. I opted to leave all badges off except for “Jeep” above the grill.

What tire size? Mine are 235/75 but yours look like maybe 245?

74Plb

Sorry for hijacking the high idle
The fender flares are Limited Trim, painted from the factory. I have the body moulding/cladding but removed all of it except for the bumpers. Currently it's at 162,000 on the odometer.
Tires are 235/75/15. When I bought it 255s were installed.
Here are the original wheels. Currently in the garage.
74Plb

arpunk

@74Plb not much to hijack. There’s only a handful of things that could cause the high idle so now I just need to go through them and see if any of them fix it. Although I’m sure having side conversation violates some sort of unwritten rule and I’m prepared to get a public lashing but at this point I really don’t care.
Also waiting on a call back from Jeep to see if they can tell me what RPM the idle should be at for a 1990 5spd.

For a 1990 your window weatherstripping is IMMACULATE! Did you have them replaced? Also thank you for keeping the window vents! I love mine and I use them often even in winter. I’m going to hold off on getting my A/C recharged and see if having four windows and two vents will be enough to keep me cool. I’m hoping I can recharge with R12 but I’ll have to see if the A/C has a leak and then do a cost comparison between R12 and R134a but it’s January in NY so that’s on the back back back burner. Where are you located?

I think I prefer the gold rims!

74Plb

Your XJ is coming along nicely. I don't think I've seen that color before!
i'm the third owner of my XJ, it was sold new in Seattle. The next buyer was in Chehalis Wa and it was neglected somewhat.
As far as I know the weather stripping is all original. The driver door seal needs some attention but other than that they are pretty decent.
I have always liked the 10 spoke turbines but the honeycomb wheels look nice too.
I'm in the PNW near Portland Oregon.
74Plb

arpunk

Nice! Sunroof, too!! Hopefully it doesn’t become a rain roof lol!

I see you’ve got the leather interior. I love my old school interior and it’s so comfortable!

Have you discovered the underhood light extension cord shindig yet? I didn’t notice until I read my build sheet.

Rogue4x4

Once again, your thread has gone into the weeds. If you guys wanna chat about trim packages and unrelated stuff, that's fine, but do it via pm or a separate thread in Cherokee chat or off topic. This will keep the thread related to the original problem and keep it relevant for people in future posts.

Please keep it on topic. Thanks

Have you done what cruiser54 suggested yet?

Nodak1

My high idle issue turned out to be the Injector O-Rings.

https://www.cherokeeforum.com/f2/hig...g-temp-266041/

arpunk

@Nodak1 I’m about to swap mine out so we shall see!