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Unread 08-23-2010, 10:28 AM   #1
Cali04LJ
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Rough Idle at stop...help before I spend money.

I live in the central valley of CA where it gets pretty hot. This last week I went wheeling up in the Sierra National Forest. I was headed up into the foothills right before a long steep climb up the grade into the mountains. I stopped to top off my gas tank when I had the problem. After getting gas, I started my Jeep (04 LJ w/ auto trans) and it was idling really rough. Felt like it was only firing on 2 or 4 cylinders. I gave it a little gas and after about 10 seconds it smoothed out. I got a little nervous so I let it sit for about 10 minutes then started it again and it did the same thing. I sat for a few minutes and everything was ok. I headed up the hill with the o/d off like I usually do and the rest of my trip was smooth sailing. My thinking is that it was a cooling issue. On this particular day it was 105 degrees. I had the a/c on until I started up the grade. I turned it off when the issue happened. The foothills are a slight change in elevation but not much (1500 to 3000). The grade goes to 7000 pretty quickly. Once I left the gas station and starting climbing everything was fine. The temperature does change drastically once you start climbing up the hill(105 to 80). Where I ended up was at 9000ft and was 70ish. My LJ has a 3.5 RE lift on 33's so I know the trans is under a load compared to stock.

I have been thinking about adding a transmission cooler for awhile and wanted some opinions. Do you think it could have been part of my issue? I could feel how hot the floorboard was thru my tennis shoes. I also thought maybe the thermostat stuck for a second then opened up which caused the rough idle.

The jeep has 44k miles. I bought the jeep with 40k miles. It was bone stock when I bought it and had never even seen a mud puddle. So the lift and tires are recent. I have been wheeling it regularly with no issues however this was the hottest day when I was climbing uphill.

So before I go and replace the thermostat and add a trans cooler, I thought I would hear what everyone has to say.

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Unread 08-23-2010, 10:30 AM   #2
2004rubicon
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did you change your plugs at 30k?
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Unread 08-23-2010, 10:50 AM   #3
Cali04LJ
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I didn't but I did check them when I bought the jeep and they were fine. I have considered doing a tune up if for nothing else to help track all the maintenance. I do all the work on my jeep.

I'm trying to see if anyone thinks it might have been a heat issue?
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Unread 08-23-2010, 10:51 AM   #4
2006_Sport
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Heat soak. Try this next time it does it. When you're at the light and it starts idling rough, floor it. Do it again at the other light. It should be gone Works for me everytime, I have the same automatic you do. It happened to me when I was at the beach, 100 degree temps.
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Unread 08-23-2010, 10:54 AM   #5
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Originally Posted by 2004rubicon View Post
did you change your plugs at 30k?
If it's got double platinum plugs like it should,you could get 90-100,000 miles out of them.
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Unread 08-23-2010, 11:10 AM   #6
Cali04LJ
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It does have platinum plugs. Not sure if that is what a LJ has stock or if they were changed. It really caught me off guard when it happened. Jeep runs like a champ everyday since I got her.
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Unread 08-23-2010, 01:49 PM   #7
unlimited4x4
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Cali04LJ, Sounds like what my 05 LJ does. I refer to it as "stumbling". Every once in a while (say once every 1 to 2 months), for no reason at all at a light it start acting like it has a misfire for a few seconds. It will work itself out shortly and then not do it for a while. I wouldn't worry about it at this point. From your post, it seems the jeep was running fine shortly after the incident. It's just something they do, maybe the heat, it's been hot here in FL too. If you haven't done so lately, take the jeep out on the interstate for 2 or 3 hours at 70 mph. Get things going at higher rpm's if you normally do mostly city driving. I always notice a difference after I do this.
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Unread 08-23-2010, 01:58 PM   #8
skouklis
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I to live in the central valley and experienced a similar issue with my chevy it was a issue with one of the injectors they might need to be cleaned or replaced.
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Unread 08-23-2010, 10:18 PM   #9
Cali04LJ
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I am a bit torn right now. My first reaction was to replace something but after it smoothed out I begin to think different. It was the first time it happened and nothing since. I wheeled in cooler weather for 2 straight days after the rough start and my jeep performed flawlessly. Maybe I should chalk it up to "who knows" and just move on. Maybe she just didn't like the heat plus the start up. I just kept thinking trans too hot issue.
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Unread 08-23-2010, 10:26 PM   #10
2006_Sport
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I told you guys...its heat soak. It happens to most 4.0s.
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