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Unread 02-06-2013, 11:40 AM   #1
ridgeback_king
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1992 YJ Wrangler 
 
Join Date: Sep 2012
Location: panama city beach, fl
Posts: 32
Another Shake at Idle Problem

Ok I'm going to outline the problem, and everything I've done to date to try and fix it so that you guys don't have to waist time guessing what I should do next.

It's a 95 YJ 2.5l

The Problem:
- I start it up and it idles nicely at 1000rpm.
- A half mile from my house at a stop sign it's still idling at 1000rpm.
- After 5 minutes of driving, any stop that I come to it idles at 500rpm and just does an annoying shake. It's not loud or anything, just more like a rumble.
- When I give it gas, it sounds and runs great. Idling is the only issue. It drops immediately to 500rpm everytime I stop.

Things I have done to try and fix it thus far:
- Checked for vacuum leaks and found a leaking intake manifold. Fixed that, idle problem remained.
- Cleaned out the entire throttle body, including the IAC value.
- Replaced the Timing Chain, Gears, and Tensioner.
- Replaced the Map Sensor.
- Replaced the O2 Sensor.
- Other items that are fairly new on the Jeep are the PCV Valve, Water Pump, fan belt.

Only remaining things that I can see being the issue:
- Instead of cleaning the IAC valve, just replacing it. I don't know how to tell if it's bad.
- Replacing the Throttle Position Sensor
- Replacing the Motor Mounts. I don't believe they've been replaced, and I can't really tell if they've gone bad. The driver side one seems to have some of the rubber padding missing.

Your opinions would be greatly appreciated, and thank you ahead of time.

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Unread 02-06-2013, 01:39 PM   #2
Reddy89
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1989 YJ Wrangler 
 
Join Date: Jun 2010
Location: , NJ
Posts: 343
Does it idle steadily at 500rpms or is shaking like it's about to stall, starving for gas?
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Unread 02-06-2013, 01:48 PM   #3
ridgeback_king
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1992 YJ Wrangler 
 
Join Date: Sep 2012
Location: panama city beach, fl
Posts: 32
It idles at 500 rpm steady... Drops to 500 and stays there.
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Unread 02-10-2013, 09:46 PM   #4
ridgeback_king
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1992 YJ Wrangler 
 
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Location: panama city beach, fl
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Nothing?
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Unread 02-10-2013, 10:14 PM   #5
Reno72
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1992 YJ Wrangler 
 
Join Date: Jan 2013
Location: Cardiff by the Sea - Glamis North, Ca
Posts: 553
Sounds like you've done a lot. Is it throwing any codes? Did you check for clogged vacuum lines? I had a clogged line at the manifold. I would check all the emission lines and sensors. I don't have the 2.5 but 500rpm sounds like a slow idles, I imagine 750 would be about right but there is no real way to speed it up with the computer. How does the fuel pump sound, does it pressure up right away? If it is going out or clogged it may show up more at idle. How is the temperature reading? There are so many sensors on these things that will affect how the vehicle idles and runs. Sorry but you've done most of what I would have looked at.
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Unread 02-10-2013, 10:23 PM   #6
ridgeback_king
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1992 YJ Wrangler 
 
Join Date: Sep 2012
Location: panama city beach, fl
Posts: 32
- It's not throwing any codes.
- I checked for vacuum leaks, but not vacuum clogs. What's the best way to find out if something's clogged. Would it be visually noticeable?
- Haven't checked the fuel pump.
- Temperature reads fine.

I'll try and take a look at these things thank you!
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Unread 02-10-2013, 11:51 PM   #7
ROTTEN
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1994 YJ Wrangler 
 
Join Date: May 2011
Location: SGF, NY
Posts: 755
Mine idles below 500. Almost to the last rpm line

I believe I have an intake leak

Try tightening up the rear bolts on the manifold. Worth a shot and free
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Unread 02-11-2013, 04:39 AM   #8
95yj0645
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1995 YJ Wrangler 
 
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Any vacuum leak on a fuel injected engine SHOULD bring your idle up. (computer senses more air adds more fuel= more RPM).. replace your iac mine is doing the same thing.
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Unread 02-11-2013, 09:11 AM   #9
Reno72
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1992 YJ Wrangler 
 
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Posts: 553
Quote:
Originally Posted by 95yj0645 View Post
Any vacuum leak on a fuel injected engine SHOULD bring your idle up. (computer senses more air adds more fuel= more RPM).. replace your iac mine is doing the same thing.
I think a leak only brings the idle up for a second till the compter refigures and adjusts. Then I beleive it will run rich, but not at all smooth. (I may be wrong, it's what i noticed on mine)
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Unread 02-11-2013, 04:26 PM   #10
95yj0645
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1995 YJ Wrangler 
 
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Im just saying replace the IAC because I know for a fact mine does not work and it is doing the exact same thing idling super floaty around 500-700 rpm. If you have access to a nice snap on scan tool you should be able to do a function test on the IAC, as well as watch your ST-LT fuel trim.
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