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Old 10-29-2010, 03:23 PM   #1
hsugene
Scooby Newbie
 
Member#: 262222
Join Date: Oct 2010
Chapter/Region: NESIC
Location: Boston, MA
Vehicle:
2011 Impreza 2.5i

Default Newbie question: 2011 2.5i noise on deceleration?

Hello everyone, this seems like an awesome community and I wish I were visiting under better circumstances. I'm hoping to tap your collective expertise on some really annoying noises coming from my new Impreza 2.5i. I have an appointment with my dealer next week but I was hoping for some independent feedback so that I can show up informed.

So first, let me provide a bit of background. It's a brand new 2011 Impreza 2.5i with less than 1000 miles on it. The noise in question occurs during deceleration but goes away as soon as I touch the gas pedal. Here's a sound clip:

http://www.squicky.org/tmp/subaru/imprezanoise.mp3

When the clip starts, I'm at about 4000 RPMs in 4th gear and I just released the gas. For the next few seconds, you can hear a rhythmic scraping sound that gets gradually louder as the car slows down under engine braking. At the 6 second mark, I tap the gas and the sound immediately goes away. And then I release the gas and it starts again.

Other potentially relevant information:

1) I get similar noises decelerating in 2nd and 3rd as well, but it's most prominent in 4th on the freeway.

2) The car is 100% stock and has been driven politely so far in accordance with proper the suggested break-in.

3) I've checked tire pressures and transmission fluid and they all seem fine.

4) The sound is a lot more obvious when the car is fully warmed up.

5) I've also noticed an intermittent rattling at idle coming from under the passenger footwell which also only happens when the car is fully warmed up (possibly related?).

I've been Googling around like crazy trying to figure this out. Maybe it's normal (in which case normal makes me sad), maybe it's an easy fix (which would be great), or maybe it's something horrible that needs to get addressed immediately (hopefully under warranty). From what I can tell, deceleration noises were common on older WRX and STI models. But I haven't been able to find any accounts of newer non-turbo models with the same issue. In any case, any feedback is very much appreciated. Thank you!

p.s. I would have posted this in a different sub-forum but, as a newbie, I think I'm only allowed to post to this one. Sorry if this is the inappropriate place for this!
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Old 10-29-2010, 04:48 PM   #2
hsugene
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Member#: 262222
Join Date: Oct 2010
Chapter/Region: NESIC
Location: Boston, MA
Vehicle:
2011 Impreza 2.5i

Default

Oh, and by the way, here's a sound clip of the rattle described above: http://www.squicky.org/tmp/subaru/idlerattle.mp3

It only happens sometimes at idle when the car is warm (never when it's cold). Sometimes I can make it disappear by rolling forward over a little bump. I'm guessing it's just a loose heat shield and I was going to get it looked at during my first oil change. The deceleration noise described before is definitely more worrisome. I'm just posting this because it might be related (and because there are so many "my car is making funny sounds" posts on the internet without recordings and I figure I'd try to set a good example ).

Thanks again!
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Old 10-29-2010, 04:57 PM   #3
RaineMan
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Join Date: Sep 2010
Chapter/Region: RMIC
Location: SL,UT
Vehicle:
2007 2.5I Wagon
Silver

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Well... IDK if this is your first Subaru or not, but statement #1: Subarus are noisy. You are going to hear things, odd things, that you won't hear in other cars.

If it is bothering you that much, mention it at the dealer and have it checked out. It's a new car, that's what warranty is for.
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Old 10-29-2010, 05:03 PM   #4
RIPEVO9
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2007 Sti "Wingless"
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Wish I could help. I got a similar scratching noise on my 07 STI when the car decelerates, but haven't figured it out. Does the sound go away when you press the clutch in?
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Old 10-29-2010, 05:46 PM   #5
hsugene
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Member#: 262222
Join Date: Oct 2010
Chapter/Region: NESIC
Location: Boston, MA
Vehicle:
2011 Impreza 2.5i

Default

RaineMan: Yeah, this is in fact my first Subaru! In fact, it's also my first new car (all my previous vehicles were purchased used) so I'm extra paranoid. But I figure that's what the internet is for I have an appointment with my dealer next week, but I suspect they won't give me a completely unbiased opinion. That's why I'm here!

RIPEVO9: It goes away if I push the clutch completely in, but pressing it lightly doesn't seem to have any effect. From what I can tell so far, the intensity of the sound is related to the amount of engine braking and how warm the car is. My suspicion is that it's a resonating heat shield, but who knows?

Anyway, I'll be sure to post whatever I learn from my dealer. Many of the related posts I've read have been regarding older cars with aftermarket parts, new transmissions, etc. Since this is happening on a stock 2011 2.5i with 840 miles, my hope is that a lot of those variables can be eliminated.
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Old 10-31-2010, 02:43 AM   #6
hsugene
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Join Date: Oct 2010
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Location: Boston, MA
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2011 Impreza 2.5i

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Folks, I think I may have made some progress on this issue. This evening, I took a drive with some friends and asked them to help me pinpoint the noise. They agreed that it was coming from the front of the car on the driver's side. So I took a look and saw this:



It's a noticeable dent (about half an inch deep) on one of the heat shields. I'm fairly certain that it's not there by design and I have no idea how it got there. But I figure that a half-inch indentation might just be deep enough to make it contact the headers and vibrate during deceleration.

By the way, this is part 22:



I'm not going to muck with this any further, as it's all under warranty, but this is giving me hope that it's just a simple heat shield issue. Anyway, I just wanted to document my findings here with the hope that it might help others with similar problems. More info to come when I visit my dealer on Monday...
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Old 10-31-2010, 02:48 AM   #7
Exarch
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Location: Colorado Springs, CO
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2012 WRX
Extremely Red

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I read the first post and immediately thought "heat shield!!!"

As #3 posted, Subaru's make some quirky noises. I came from a Honda/Toyota family, the first three weeks of ownership were harrowing!

Good excuse for some new exhaust bits imo!!!!

Looking forward to hearing what the resolution ended up being!
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Old 10-31-2010, 03:03 AM   #8
hsugene
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Member#: 262222
Join Date: Oct 2010
Chapter/Region: NESIC
Location: Boston, MA
Vehicle:
2011 Impreza 2.5i

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Yeah, these past few weeks haven't been particularly relaxing for me (aside from the noises, there's the little matter of signing away thousands of dollars...eek!). But hey, I figure it builds character
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Old 11-01-2010, 02:19 PM   #9
hsugene
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Member#: 262222
Join Date: Oct 2010
Chapter/Region: NESIC
Location: Boston, MA
Vehicle:
2011 Impreza 2.5i

Default

Ugh. So, I took it to my dealer this morning and they said it didn't sound like anything to worry about. At least, that's what the service advisor said. The technician that rode along with me seemed to think it was unusual and wanted to compare it to another 2011 Impreza (but unfortunately they did not have any on the lot).

They also tightened up the heat shields but that didn't have any effect on the noise. I asked about the dent and they said it almost certainly wasn't deep enough to contact anything underneath.

Oh well. I guess I can just wait and hope that it goes away as everything settles in. I think, when I have some free time, I'll try loosening the heat shield to see if it has any effect on the sound. Maybe I'll take it by an independent shop for a second opinion. I don't know.
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Old 11-04-2010, 02:52 PM   #10
hsugene
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Join Date: Oct 2010
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Location: Boston, MA
Vehicle:
2011 Impreza 2.5i

Default

So I'm back from yet another visit to my dealer. I got the same technician, and this time around he got another technician to ride along. They both heard the sound again, but I think the conclusion was "we're not exactly sure what it is, but we don't think it's a problem." I'm not sure if that's an answer that I'm comfortable with. I've read some other threads here with similar noises coming from defective clutches or differentials, so this is still freaking me out (FYI, I tried the old WRX trick of changing front/back tire pressures with no effect).

Before they gave the car back to me, they said that they adjusted the heat shields (based on what I see, this means they bent the edges a bit to make sure they're extra tight). Maybe I'm hallucinating, but I think the sound is louder now! Unfortunately, it's raining right now so it's hard to tell for sure. But if it really is louder (which I'm kind of hoping for), that would be conclusive evidence that it's a heat shield issue (because they didn't adjust anything else).

I made a new appointment for Monday morning. I'm hoping that it'll be the last! I think this time around, I'm going to ask them to just pull all the heat shields and take a drive to determine if they are actually the cause of the sound (maybe I should have asked for this already).

Also, I made a better recording of the sound: http://www.squicky.org/tmp/subaru/scrapey.mp3

Anyway, if anyone has any additional thoughts, they'd be much appreciated (even if it's just another "sheesh, it's a normal Subaru noise, deal with it" ). Thanks!
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Old 11-08-2010, 01:28 PM   #11
hsugene
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Join Date: Oct 2010
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Location: Boston, MA
Vehicle:
2011 Impreza 2.5i

Have a Nice Day? The solution?

Okay, so I think I've convinced myself that my deceleration noise is the same one that's been described many times before in these forums.

Like others before me, I gave the tire pressure trick a go (setting the front tire pressures higher than the rears). The first time I tried this, the noise did not go away. However, it did change: instead of starting at 3500rpm, it started at 4000rpm. With this in mind, I "tuned" the noise away by tweaking the pressures. Where I have it now (38F/34R), it seems to crop up very lightly at around 4500rpm. That's a lot better than having it scratching all the way down to 2500rpm like it was doing at the recommended 33F/32R.

Anyway, I discussed these findings with my Subaru service advisor this morning, and he was genuinely stumped by this (but he was glad that he didn't have to deal with my complaining any more). He did state that running 38F/34R was not significant enough of a difference to cause any issues with the center differential over time.

I'm glad that this simple fix somewhat resolves the problem, but I am left wondering if my car is actually a bit out of adjustment or if this is a fundamental property of the Subaru drivetrain. I somewhat suspect the latter since (1) it's a recurring issue that's been mentioned for a variety Subaru models over the past decade, (2) from what I can tell, there hasn't really been a conclusive fix for the issue (the closest being a flywheel replacement in 2002, but given that newer stock Subarus exhibit the same problem with the new flywheel, I wouldn't count that as an actual resolution).

What I can say is that I'm astounded by how sensitive the sound is to tire pressures and temperature. To me, this suggests that it's a simple but annoying resonance issue that isn't causing anything more than psychological damage. My suspicion is that this noise exists in some form in any Impreza/WRX/STI/Forester. Some people are probably lucky to have their cars tuned so it happens above redline or below idle (e.g., never), but I'm guessing that you could induce it by tweaking tire pressures.

Anyway, this is my rant/solution/conclusion. I'm obviously far from being a Subaru expert, but I think my conclusion that "it's just a Subaru noise" signifies my graduation from Subaru newbiehood
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