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Unread 04-19-2013, 08:18 AM   #1
850WJ4x4
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Wj 4.0 Rough Idle

I have been trying to track down a problem with my 4.0 I6 In my WJ as of lately. When the engine is completely cooled down and I go to start it up in the mornings it idles rough once its warmed up it runs great for the most part every once in awhile at a stop light I will feel a slight stagger. There is no engine noise. I do have a Large Evap Leak but I dont see how that would cause a rough idle. Also before its warmed up if I accelerate initially it sort of staggers but then seems to accelerate fine with no loss in power. Any suggestions would be much appreciated. I have already replaced the spark plugs. Oil has been changed on schedule as well. Where should I start? No other engine codes other than EVAP Leak. Help!?

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Unread 04-19-2013, 08:21 AM   #2
doityourselfMM
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How have you diagnosed that you have a 'Large Evap Leak ', if you are not getting any codes?
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Unread 04-19-2013, 08:24 AM   #3
850WJ4x4
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Woops. Just edited my post. I had meant I have no other Engine codes other than the EVAP Leak Codes.
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Unread 04-19-2013, 08:26 AM   #4
doityourselfMM
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No problem. Which code, specifically, are you getting?

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Originally Posted by 850WJ4x4 View Post
Woops. Just edited my post. I had meant I have no other Engine codes other than the EVAP Leak Codes.
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Unread 04-19-2013, 08:26 AM   #5
850WJ4x4
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By Rough Its like a shudder in the engine bay and when I initially try and accelerate while the engine is cold it shudders but after about 1 sec of accerlating its gone as long as I am on the gas until it reaches operating temperature.
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Unread 04-19-2013, 08:29 AM   #6
850WJ4x4
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p0455
p0305

Large and small Evap Leak. Which Im sure Im getting both codes due to the large evap leak where ever it is. I have tracked it down back to the charcoal canister I'm pretty sure just haven't pulled it all down and replaced the lines. Don't see how that would cause the issue I'm having though but then again I'm not sure.
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Unread 04-23-2013, 09:37 PM   #7
HOSTED67
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p0305 is a misfire on cylinder #5. That is probably your shudder.
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Unread 04-24-2013, 06:20 AM   #8
cjcyr8
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I had this EXACT same problem a couple years ago......If you have a 4.0 I-6, carefully check the fuel injector wiring harness; follow it from the front of the valve cover to the rear of the engine....There is a cylinder head stud/bolt at the very back of the engine (drivers side behind valve cover) this stud/bolt threads rubs through the harness, short circuits the wires and causes rough idle, misfires, hesitation and misfire/open circuit codes, including P0305 you mentioned. The symptoms sometimes begin after the engine is hot or has been running on the highway for awhile, and often come and go...It will take more than just a quick visual inspection....If the harness is resting upon this stud (or near it for that matter), if you don't allready have this problem eventually you will. I repaired the wire, wrapped the entire in harness in nylon loom, and put piece of vacuum hose over that stud...problems solved...

below is link to a picture from Swifty, scroll down a bit you'll see what I'm talking about:

http://www.jeepforum.com/forum/f310/...issue-1488591/
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Unread 07-06-2013, 10:13 AM   #9
850WJ4x4
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Replaced all my plugs and gaped them no misfire. But I still have the shudder before operating temp.
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