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Old 11-29-2011, 09:39 PM   #1
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new 2012 JKRubicon- odd cold exhaust whine?

Hi guys - new member.

I just bought a new 2012 JK Rubicon 2dr auto. 500 miles so far. It's great - such improvements over the years. I've owned OG renegades as well as a sport back in 1995.

One odd thing that I noticed was when accelerating out of my neighborhood (low gear, higher rpm starts) I get a whine or higher pitch gear-growl not unlike the sound of a ducati motorcycle. After 3-4 minutes of normal driving that effect is gone. If I pull up to a red light, when it turns green and I take off the effect is no longer there like it was when I pulled out of my street. It seems to go away when the jeep warms up.

If I park for 30-40 minutes it will happen again upon take-off. It's at about 2500 RPM give or take. Seems like a cool car symptom. I actually first though it was in the tranny (like dry gears) but I think it's exhaust or exhaust manifold.

My question is "Is this normal - or has anyone seen this?". I went to the dealer to test a new car but their only auto was a JKU and it didn't demonstrate the same problem at all.

I have an appt set up for monday but the service guy hear it and said "it could just be the nature of YOUR rubicon, but I do hear it" (odd comment)

Thanks!

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Old 11-29-2011, 09:59 PM   #2
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I hear a "tinny rattle" sound to my exhaust at about that same RPM and I just chalked it up to the acoustics of the exhaust system and perhaps something to do with that whacky exhaust loop. Does that description match what you are hearing as well?

Mine is there still slightly after the car is warm, but is far less pronounced. I attributed that to the emissions control hardware changing the amount of air to fuel during warmup and figured it was all pretty much exhaust and emissions related and normal for the new Pentastar "Jesus" engine.

I am curious to know what the dealer has to say about yours if we are indeed talking about the same noise.

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Old 11-30-2011, 10:13 AM   #3
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I'll keep you posted after my visit - Unsure if tinny is what I hear - more "motorcycle-ish". ALmost makes your engine sound like a 4 banger". But yes - it does sound like the ECU makes changes after the car is warmed up. Obviously not a carbureted car - but it nearly disappears about the time a choke would shut off, so your theory is accurate.

I didn't hear it in the Unlimited i tested because I'm sure the exhaust loop is longer or "different" shape in that truck.

Cheers.
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Old 11-30-2011, 10:46 AM   #4
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Quote:
Originally Posted by Ericpso View Post
I'll keep you posted after my visit - Unsure if tinny is what I hear - more "motorcycle-ish". ALmost makes your engine sound like a 4 banger". But yes - it does sound like the ECU makes changes after the car is warmed up. Obviously not a carbureted car - but it nearly disappears about the time a choke would shut off, so your theory is accurate.

I didn't hear it in the Unlimited i tested because I'm sure the exhaust loop is longer or "different" shape in that truck.

Cheers.
I have it too on my Unlimited, it was surprising to hear (especially since my old Wrangler with the 3.8L had a nice rumble to it). But we should remember that this is a DOHC engine so it's expected.
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Old 11-30-2011, 08:13 PM   #5
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Originally Posted by CombatChuk View Post
I have it too on my Unlimited, it was surprising to hear (especially since my old Wrangler with the 3.8L had a nice rumble to it). But we should remember that this is a DOHC engine so it's expected.
Are you getting the motorcycle sound? Do DOHCam motors high a higher pitch "chainsaw" note?
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Old 12-01-2011, 02:13 PM   #6
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Originally Posted by Ericpso View Post
Are you getting the motorcycle sound? Do DOHCam motors high a higher pitch "chainsaw" note?
They typically do.
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Old 12-01-2011, 04:22 PM   #7
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Does this sound come from the engine compartment, under the drivers seat, rear of vehicle or from the dash area?
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Old 12-02-2011, 10:52 AM   #8
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Seams like under the front seats. Or by the footwell - so exhaust location.
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Old 12-08-2011, 11:38 AM   #9
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So I had my service visit on this issue and it turns out to be a normal cold sound based on the VVI technology. Closing down valves until the motor warms up - it gives it a honky "2 stroke" sound for the first few miles.

I also learned that it will be less so in the warmer months, and worse in the cooler months. I've only had mine for a month - and it's been @ss cold here.

We drove a new one as well and the awesome sales guy knew about the cold engine honkiness before we even took off. It made a very similar sound to mine - maybe a slightly different musical key, but the same essential tone.

So my mind is at ease. For the record its a cold engine sound that occurs between the rev count of 2500 to 2800 for the first 2 miles.

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