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Unread 10-02-2013, 09:53 PM   #1
kpatterson00
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Join Date: Oct 2013
Location: duluth, ga
Posts: 22
New To Me 4.7HO WJ P0455 Code With Knock

First off let me saying I am no newby. I have built several 1 ton jeeps in the past. I bought this jeep strictly for work. I got a solid deal on it knowing that the oil pressure is good, runs smooth, not loss of power and extremely clean being an 02.

Now the issue: No check engine lights but I did the key trick upon test driving it and found a P0455 (vacuum leak) It does not run or idle rough, however it makes a knock similar to this.
Anyone dealt with a similar issue? I have no problem pulling it apart and checking the timing chain tensionors. Want some first hand experience before I do so. Thanks in advance.

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Unread 10-02-2013, 10:06 PM   #2
coloradowjowner
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2002 WJ 
 
Join Date: Jan 2013
Location: Fort Collins, Colorado
Posts: 207
My 02' 4.0 popped this code. Changed the fuel cap, and it never came back.
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Unread 10-10-2013, 09:40 AM   #3
kpatterson00
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Join Date: Oct 2013
Location: duluth, ga
Posts: 22
Well I bought a stethoscope. hard to tell but it sounds like its come from the passenger side valve cover closer to the fire wall. It makes the noise at cold idle then stops at 2k RPMS. When warm it always knocks, faster with higher RPMs. Any guesses before I take the passenger valve cover off? I added half a can of seafoam to the oil with a couple hundred mile I dont hear any improvement. HELP!
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Unread 10-10-2013, 09:07 PM   #4
Bandit84
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2004 WJ 
 
Join Date: May 2008
Location: MN
Posts: 212
Could be a thrown rocker arm. I've heard of that happening before.
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Unread 10-16-2013, 06:38 PM   #5
kpatterson00
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Join Date: Oct 2013
Location: duluth, ga
Posts: 22
Sound doesn't get loud until it warms up then it increases with rpms. I don't think it a thrown rocker arm. Power is good and idles very smooth.
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Unread 10-16-2013, 07:58 PM   #6
2ndhandWJman
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2003 WJ 
 
Join Date: May 2013
Location: Baltimore, md
Posts: 271
cracked exhaust manifold or Y pipe leak?
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