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high idle in park and neutral

S

Spongebob91785

NAXJA Forum User
Location
Louisville,ky
i have an 90 xj and when you start it in park it runs at about 2100 rpm it does the same in neutral but when you put it in anyother gear it idles fine does anyone know what could be wrong with it
 
vaccum leak?

The police package high idle switch revs it to about 1100 or so.
Spins the alternator for the accessories and keeps the oil pressure up.
Kinda unique, never seen it 'cept in a Jeep.
 
hi idle just in a jeep?????
dude - its in fire trucks, ambulanes, cop cars. every viechle thats gona sit on scene for a while will have an hi idle option.
 
does the hi-idle start when the engine is cold?? and is it lower in gear because the resistance of the torque convertor? if you idle in gear will it work up to 2100 rpm again? mine does the same thing EXCEPT at cold idle.. as it warms up it works higher.. this has ben since the engine got wet from a degreasing sesssion.. look at the TPS.... they do not react well to water..
mike
 
kc7bur said:
vaccum leak?

The police package high idle switch revs it to about 1100 or so.
Spins the alternator for the accessories and keeps the oil pressure up.
Kinda unique, never seen it 'cept in a Jeep.
Click to expand...
Next time your under the hood, pull off the big brake booster vacuum hose. That dudes gonna race.

Shoot some starter fluid around at the lines and connections and listen for a change in RPM, that'll be a leak.
 
did you clean your TB? Mine did the same thing after I took the TB off and cleaned it. Turned out that over the years and 316k miles the butterfly and TB bore had become coverd with gunk. This pluged the small gap between the two. Someone (the PO) moved the little stop screw out to comp this. So after I got it cleaned the gap was now to large and alowing too much air. I had to reset the little set screw on the TB to fix this. Good luck DH
 
i would also clean your IAC Valve, located on your throttle body. i had a fluctuating rpm problem and high idle when first fired up and i cleaned the pintle or whatever its called w ith some carb/choke cleaner fixed the problem right up
 
ditto to the above regarding the IAC, its just good maintenance. But I'd still go hunting for a vacuum leak, its your most likely culprit.

just... do one thing at a time, so as to troubleshoot properly.
 
Not to hijack the thread,
But what is the IAC valve?

I have a 1990 that has a occasional high idle at start up, but I usually turn it off and then restart it again and the idle drops to normal.

I thought I should go looking for the cause sometime, because maybe someday, turning off the XJ and restarting might no cure it!!!!!!

Thanks,
Bob
 
DownhomeMoto said:
did you clean your TB? Mine did the same thing after I took the TB off and cleaned it. Turned out that over the years and 316k miles the butterfly and TB bore had become coverd with gunk. This pluged the small gap between the two. Someone (the PO) moved the little stop screw out to comp this. So after I got it cleaned the gap was now to large and alowing too much air. I had to reset the little set screw on the TB to fix this. Good luck DH
Click to expand...


Haha, I would hope he had this fixed by now, its been over 5 years since the last post.
 
Begster said:
Haha, I would hope he had this fixed by now, its been over 5 years since the last post.
Click to expand...

*facepalm*

zombie threads for the win...

For the fella that asked, the IAC sits next to the TPS on the throttle body. Use the search tool to narrow it down more if you need to, it is worth knowing tho.
 
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