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Unread 01-25-2013, 09:46 AM   #1
SAbbott812
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1998  
 
Join Date: Jul 2012
Location: Aurora, Colorado
Posts: 38
Idle Issue at a stop

Hi everyone, it's me again.
It is not a huge issue as of yet but, I would like to keep it from becomming an issue. MY GC will run great when cold but, occasionally when warm and you stop at a light after driving a bit there will be very slight fluctuation in the RPM's and the truck will shake a bit. Sometimes it does it once, sometimes it does it over and over again. I thought it was the IAC so I cleaned it and it seemed to help but, then it came back. (I did this over and over for a bit.) Finally I replaced the IAC at NAPA. The problem has not gone away and it is not really getting worse. I would just like to stop it. Any suggestions? Could it be the TPS? Thanks for your help!!!

Sandy

Pertinent info:
98 Jeep Grand Cherokee Laredo L6
189,000 miles (approx)
top end rebuild (with engine mounts) in 2007
new springs, tranny mount, and bushings 2012

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Unread 01-25-2013, 09:52 AM   #2
FAlfani81
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1993 ZJ 
 
Join Date: May 2012
Location: Farmingville, New York
Posts: 341
Torque Converter?
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Unread 01-25-2013, 10:14 AM   #3
bigbill888
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1996 ZJ 
 
Join Date: Nov 2009
Location: michigan
Posts: 968
Heater control in defrost position when this is happening?
__________________
96 ZJ Laredo, 4.0, 242, 230K
95 ZJ Limited, 4.0, 242, 140K
98 XJ Sport, 4.0, 231, 140K
All work well
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Unread 01-25-2013, 10:23 AM   #4
SAbbott812
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Posts: 38
@bigbill888 I don't believe that it is but, I will keep an eye on it and let you know.

@FAlfan81 Will the TC effect the idle at a stop? Sorry to ask that question but, I really do not know.
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Unread 01-25-2013, 10:25 AM   #5
FAlfani81
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1993 ZJ 
 
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Location: Farmingville, New York
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Quote:
Originally Posted by SAbbott812 View Post
@FAlfan81 Will the TC effect the idle at a stop? Sorry to ask that question but, I really do not know.
It could if its locking up. Kinda like driving a 5spd and not pushing the clutch all the way and leaving it in gear when you stop.
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Unread 01-25-2013, 11:31 AM   #6
SAbbott812
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Location: Aurora, Colorado
Posts: 38
Could it be an O2 sensor?
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Unread 01-25-2013, 11:40 AM   #7
PolkaPower
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Sounds like it might be a sensor since it only does it after warm up.
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Unread 01-25-2013, 12:27 PM   #8
Donnyd21
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1998 ZJ 
 
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Yes it could be a O2 sensor.
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Unread 01-28-2013, 10:59 AM   #9
SAbbott812
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Ok, I drove it around again this weekend. It is not affected if the radio or the heater / defrost is on. The headlights also do not make a difference. (Not sure that is important, just an observation). I am also wondering if there could be a short somewhere in the wiring on the IAC. Frustrated as I am not getting a check engine light or anything. I should have it read for codes though.

BTW, how many O2 sensors are there? Anyone know which one might be a culprit?
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Unread 01-28-2013, 12:02 PM   #10
dougmorgan99
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1998 ZJ 
 
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Location: Tulsa, Oklahoma
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Quote:
Originally Posted by SAbbott812 View Post
Ok, I drove it around again this weekend. It is not affected if the radio or the heater / defrost is on. The headlights also do not make a difference. (Not sure that is important, just an observation). I am also wondering if there could be a short somewhere in the wiring on the IAC. Frustrated as I am not getting a check engine light or anything. I should have it read for codes though.

BTW, how many O2 sensors are there? Anyone know which one might be a culprit?
Your 98 should be OBDII so it should have 2.
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Unread 01-28-2013, 02:48 PM   #11
SAbbott812
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Location: Aurora, Colorado
Posts: 38
Is there a way to check the O2 sensor or will it throw a code?
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Unread 02-10-2013, 09:01 AM   #12
SAbbott812
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1998  
 
Join Date: Jul 2012
Location: Aurora, Colorado
Posts: 38
OK new update. I was driving down the highway yesterday and for some reason the tach jumped about 500-700 rpm but then returned to normal and did not do it again. The idle is still rough. I have not replaced anything besides the IAC that I purchased at NAPA. Any further thoughts?
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