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  #1  
Old March 2nd, 2019, 21:52
MickeyS MickeyS is offline
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Low idle while coming to complete stop?

96 XJ runs great otherwise. I have low-ish idle while coming to a dead stop on the brakes (can dip down to 690) but once stopped, goes back up again to 720-750 idling in drive. idle is normal 750-800 in park. coming to a stop you can hear the rpms drop and feel it a bit. gets a little better when the engines good and hot.

obd2 absolute manifold pressure reads 10-13 in hg depending on temp but usually between 11-12 which the engine at 210. checked for leaks but can't find any on the manifold but maybe i'm missing something.
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  #2  
Old March 3rd, 2019, 07:20
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Re: Low idle while coming to complete stop?

Clean the Idle Air Controller. If the symptoms persist, replace the IAC. Genuine Jeep parts cost more, but work better and last longer.
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Old March 3rd, 2019, 07:41
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Re: Low idle while coming to complete stop?

http://cruiser54.com/?p=60
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  #4  
Old March 3rd, 2019, 07:57
Heavyopp Heavyopp is offline
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Re: Low idle while coming to complete stop?

My 96 does the exact same thing but it isn’t consistent — sometimes it’s just fine

I do have a cracked exhaust manifold — figured no sense in chasing the low idle till I change out the manifold
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Old March 3rd, 2019, 08:00
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Re: Low idle while coming to complete stop?

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Originally Posted by Heavyopp View Post
My 96 does the exact same thing but it isn’t consistent — sometimes it’s just fine

I do have a cracked exhaust manifold — figured no sense in chasing the low idle till I change out the manifold
Totally unrelated, but do what you gotta do.

That cracked exhaust manifold is not causing your low idle.

Cleaning throttle bodies and IACs is considered a maintenance item............
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  #6  
Old March 3rd, 2019, 08:04
MickeyS MickeyS is offline
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Re: Low idle while coming to complete stop?

i have cleaned the iac but the problem persists.

i tried replacing it with an aftermarket one, but immediately got iac codes and a 2000 rpm idle so i figured that was a chinese dud and returned it. i guess the next step is trying a mopar sensor?
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Old March 3rd, 2019, 08:11
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Re: Low idle while coming to complete stop?

Clean the throttle body per the link!!!!
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Old March 3rd, 2019, 08:19
MickeyS MickeyS is offline
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Re: Low idle while coming to complete stop?

yep sorry i'm not making it clear. the entire throttle body/iac etc is clean/spotless
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Old March 3rd, 2019, 08:33
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Re: Low idle while coming to complete stop?

Okay then.
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  #10  
Old September 22nd, 2019, 22:28
MickeyS MickeyS is offline
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Re: Low idle while coming to complete stop?

Still having this issue. To bring it up to speed:
New iac
Cleaned throttle body
Recent battery/alternator replacements
Recently replaced fuel filter with wix

Would a crack on the manifold cause this? Coming to a stop engine can dip to 690 before recovering in a few seconds where it idles between 720-750. 720 a bit low.
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Old September 23rd, 2019, 04:42
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Re: Low idle while coming to complete stop?

Genuine Jeep IAC ? A cracked exhaust manifold should have no effect on the idle. If the engine does not stall, I wouldn't worry about it.
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Quote:
Originally Posted by bimmerjeeper

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  #12  
Old September 23rd, 2019, 10:38
MickeyS MickeyS is offline
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Re: Low idle while coming to complete stop?

It feels like something's amiss but yeah, it's not throwing codes. I figured wait until it gets worse and then it would be easier to diagnose, but I don't drive it enough. I'm going to put a pack of $5 injector o rings on this week and triple check vacuums going to throttle unit, see if it helps at all.

I just don't want it to cause a bigger issue down the line, as it seems to be running a bit lean and lower mpgs. (13 town)
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Old September 23rd, 2019, 15:37
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Re: Low idle while coming to complete stop?

If it is an automatic transmission, the clutch in the torque converter could be staying locked.
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  #14  
Old September 23rd, 2019, 21:59
Heavyopp Heavyopp is offline
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Re: Low idle while coming to complete stop?

Mine is cured but I don't know exactly what did it -- Noticed the problem went away after a can of Bk 44 injector cleaner was run through the tank

Here is what I did since the last post in this thread by me:

Replaced cracked exhaust manifold
Total cleaning of intake manifold and IAC while it was off
Added DEI injector insulation kit -- New Injector O rings installed with the kit
built and installed a heat shield for under the intake manifold
Replaced motor mounts
Ran a can of BK44 injector cleaner thru the system

At this point low idle issues are gone
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  #15  
Old September 23rd, 2019, 23:31
MickeyS MickeyS is offline
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Re: Low idle while coming to complete stop?

that's almost exactly my attack plan once the weather cools down here. get that damn manifold off swap the mounts and super deep clean the fuel/intake system. I will order a can of that bk44. looks like good stuff the injectors are 180k miles old, but I have run chevron and seafood through it before.
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