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Old 10-14-2012, 08:34 PM   #1
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2012 JKU rattling + lost of power

hi,

2012 JKU pentastar

I have a light rattle on passenger side on acceleration from 1st to 3rd gear. Feels like shaking a coin in a pepsi can. I noticed it is combined with a lost of power, motor hesitation and harder downshifting when using the tapping shifter.

Interestingly, when it is raining or humidity level is high, the rattle disappears and the jeeps feels so much more powerful and shifts better. I am sure it is the way the new engine is supposed to perform.

Dealer does not want to do anything about it.

i am looking for advices.

please help

thanks

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Old 10-14-2012, 08:43 PM   #2
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I have the same. No answer for you though.

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Old 10-14-2012, 09:24 PM   #3
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what in the hell could explain humidity or rain can make a vehicule running better and stop a rattle ?

it seems hard to explain
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Old 10-14-2012, 09:27 PM   #4
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Originally Posted by Mowgli25
I have the same. No answer for you though.
did you go to the dealer ?

i cant let this go ....

is it the sign of a dying head ?
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Old 10-14-2012, 10:12 PM   #5
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Kind of sounds like spark knock.
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Old 10-14-2012, 10:30 PM   #6
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You don't mention if it is an automatic or stick, or if it has any modifications or the mileage, recent changes, etc. It's really hard to diagnose a sound over the internet with limited information.

Couple of easy checks.

1. Make sure you are not low on oil.
2. Try running a couple tanks of premium gas through it. (If it's spark knock, this will make it go away.)
3. Pick up a cheap code reader ($60-80) and see if the OBD II software has any codes stored. (If it's been to the dealership to check it out, they have probably already done this.)

Mike
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Old 10-14-2012, 10:35 PM   #7
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Quote:
Originally Posted by patrickp
hi,

2012 JKU pentastar

I have a light rattle on passenger side on acceleration from 1st to 3rd gear. Feels like shaking a coin in a pepsi can. I noticed it is combined with a lost of power, motor hesitation and harder downshifting when using the tapping shifter.

Interestingly, when it is raining or humidity level is high, the rattle disappears and the jeeps feels so much more powerful and shifts better. I am sure it is the way the new engine is supposed to perform.

Dealer does not want to do anything about it.

i am looking for advices.

please help

thanks
Sounds almost like pinging or spark knock. Maybe bad gas or a bad knock sensor. The fact that it improves with high humidity supports that (high humidity reduces detonation... people used to put water injection on cars back in the 70s to improve performance). Try a tank of mid grade or premium and see if it clears up. If it does then comes back, take it back to the dealer and demand that they fix it. The owners manual recommends 87 octane and if it won't run properly on it, something is wrong.
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Old 10-14-2012, 11:17 PM   #8
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Quote:
Originally Posted by onetraveller View Post
You don't mention if it is an automatic or stick, or if it has any modifications or the mileage, recent changes, etc. It's really hard to diagnose a sound over the internet with limited information.

Couple of easy checks.

1. Make sure you are not low on oil.
2. Try running a couple tanks of premium gas through it. (If it's spark knock, this will make it go away.)
3. Pick up a cheap code reader ($60-80) and see if the OBD II software has any codes stored. (If it's been to the dealership to check it out, they have probably already done this.)

Mike
automatic , 2000 miles , plain stock.

I just want to know where to search.



1)Not low on oil.
2) Ive runned premium gas . this is my third tank and it is still de same.
3) For the codes, i tried the 3 quick on-off and no code has shown up
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Old 10-19-2012, 08:35 PM   #9
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Originally Posted by patrickp View Post
automatic , 2000 miles , plain stock.

I just want to know where to search.



1)Not low on oil.
2) Ive runned premium gas . this is my third tank and it is still de same.
3) For the codes, i tried the 3 quick on-off and no code has shown up

somebody must have been experiencing the same and have a solution ?
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Old 10-29-2012, 10:24 PM   #10
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i tried mid grade gas but it is not doing it. dealer says everything is fine but obviously its not

im sure some people habe solutions for this
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Old 10-30-2012, 07:42 AM   #11
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Find another dealer to look a it.
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Old 10-30-2012, 09:49 AM   #12
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Time for another dealer.
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Old 11-12-2012, 02:12 AM   #13
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I have a 2012 jku sport manual and have the same problem. I haven't figured it out yet.
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Old 11-12-2012, 03:44 AM   #14
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When humidity is very low an engine is more likely to have spark knock.

http://www.fuelcertification.com/doc...gine_Knock.pdf
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Old 11-12-2012, 03:49 AM   #15
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Dunno if mine is experiencing knock, but if you're talking about some strange sound, mine sounds like there's a rattle behind the dashboard upon acceleration. I just figured it's some sort of vibration of something caused by resonance.

Personally, I've always felt as if my 3.6L was a weak engine, so maybe it's the same issue you're having, I dunno...

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