When you spray carb cleaner around the base of the throttle valve does the idle speed change?

 

Did you check the O2 sensor fuse under the hood when you changed it out?

 

An old cat can cause a slow return to idle. While sitting still rev your engine to 2k-2.5k and release pedal do this several times.

Also when your letting the jeep warm up in the am does it idle down to 800 when it gets warm.

 

i did, that was my seal test.


just checked it, its good, but swapped it just to make sure. no changes


that sounds bang on. when i rev to just shy of 2k and let off it jumps a couple hundred rpm and slowly comes down.
the idle does seem just a little slower then normal, but not much.

maybe i need a new cat.

 

my bet its gonna be your main cat and i believe its walker has replacement cats for around $250, you just gotta do a search for them. a failure cat wont throw a code right away. it sometimes throws O2 sensor codes first. see if you can unbolt yours and take a visual in it to see the condition.

 

cat replaced yesterday.
220k driven to see if it settles.
its ~better~ but still hanging at 1200-1300 rpm when i let off the pedal.
i wanted to say it feels like the tranny is hanging a little, but it does it when i pop it into neutral too.

sigh.

 

And one last thing. Have you seafoamed through a vac line? And any na Sayers don't start bashing please

 

nope, ive heard of seafoam, never seen it before though.

just for ****s and giggles i put the stock injectors back in and reset everything. no changes same problem.
im really really stumped.

 

It's sounds like a dirty system. It's not the end of the world BUT. Click on the seafoam link in my signature and it'll tell you everything you need to know. Give it a whirl it'll smoke your neighborhood out and smooth out idle and such and can help you idling issue

 

Alright, here we go.

did the cleaning as you posted. didnt actually smoke much but it does idle a little nicer.

Anyway, back to the original problem, its still taking too long to return to idle about half the time:
a few observations:
im starting to think its running too rich, as my tailpipe is black, which would also explain the slow return to idle... So i unplugged the o2 sensor to see if it was swapping between open and closed loop ( which would explain the slightly bouncy needle) but alas, it still hangs.
i was hoping it was a bad ground, but its not.. or at least not there.


help guys, someone has to have another guess.

 

You might want to reset the ecu. I had idle problems after a dead battery...it worked for me: https://www.cherokeeforum.com/f2/jee...ocedure-46047/

 

already been done, its about 25 starts into it, not getting any better or worse.


Any electric guru's on here? im starting to wonder why the thing is so sure its running lean and is pumping extra gas in to compensate. my tailpipe is showing me its rich.
it has a brand new O2( and the one before it that i replaces because of all this was probably fine.)

perhaps a slightly goofy ground to an O2, or even the TPS? not enough to throw a code, but enough to play with the sensor readings?

 

Ok I know this thread is several years old, but I saw it when mine was having issues so its definitely still helping other jeepers out. Mine was having this issue, would take forever to return to a normal idle, especially once it warmed up (like hanging at 1250-1700 rpm before SLOWLY returning back down to 900 or so). Was running too rich and hotter than it should have. When I unplugged my AIC it would return to idle normal when warm but was hard to start. I cleaned that, checked for vaccuum leaks, checked my MAP sensor, still nothing. Turned out to be an easy fix, the temp sensor for the computer on the rear of the block (not the one by your thermostat housing that runs your temp gauge). The wire going to it had rubbed almost completely through. I cut it and put a good crimp connector on, started the jeep, and she runs like new. Just thought I would share so we could have one more documented case that was solved on this issue.

 

Ummmmmmmmmmmmmmmmm, I think you got those sensors actual function backwards, nice try tho.

"When I unplugged my AIC it would return to idle normal when warm"
(Idle Air Control)
This is your clue.

 

I know this thread is old, but I have been having this exact same problem and I cannot figure it out on a 2001 i4