Weird noise when accelerator passes a certain point

supraking · 06-25-2009, 11:51 PM

Had my 128 a week. Just today I noticed that when I push down my accelerator to a certain point, I hear a loud click (more of a KA-CHINK but not so metallic) come from under the car (it would seem, I'm driving so I dunno). Then when I bring the accelerator back up past this same point, I hear a similar noise (as if something first engaged and then disengaged, or sprung and then unsprung).

Anyone have any idea what this could be? Doesn't do it when I'm in park (and not in gear). Tranny maybe? Someone else mentioned the engine mounts might need to be looked at? I'm calling BMW tomorrow and we'll see what they do, hopefully they know what the problem is and can fix it quickly.

Manual transmission..

jeremyc74 · 06-25-2009, 11:57 PM

Kickdown swich maybe? Does it happen to downshift about the same time you hear this noise?

supraking · 06-26-2009, 12:09 AM

It's a manual (just added that to the original post).

supraking · 06-26-2009, 09:05 AM

I just realized that it seems to be coming from the exhaust pipe. I looked into the pipe and saw a flap in there that I think is opening and closing when throttle reaches a certain point, I assume to eliminate back pressure? I saw a post about this a while ago, I'm gonna go try and find it. If anyone knows what I'm talking about please post a link.

jeremyc74 · 06-26-2009, 09:59 AM

Quote:

Originally Posted by supraking

It's a manual (just added that to the original post).

Oh ok. I saw you said something about "in park" and assumed it was an Auto.

You're right about the exhaust flap. It opens up once you reach a certain point and changes the sound of the car. It's really nice if you've got catless downpipes on the car. It maintains a "near stock" sound for normal driving, and then screams when you open it up.

If you search for "golf tee mod" you'll see that there's a way to make it stay open all the time if you want.

lib · 06-26-2009, 10:13 AM

It's the flap in the exhaust that closes off one of the pipes. I began to notice the same sound a month or two ago and it's surprisingly loud now.

When I took my car in for the first dealer oil change earlier this week I mentioned it to the SA along with another unrelated issue. At the time I didn't make a big deal about it but wanted to mention it in case it was something more serious. After they had some time to look at it my SA ordered a new muffler (the flap is apparently integral) and we're replacing the whole thing next week.

If it happens again I'll probably do some version of the golf-tee mod to disable the flap.

06-25-2009, 11:51 PM	#1
supraking Captain 49 Rep 759 Posts Drives: 128i Coupe 6MT Join Date: Apr 2009 Location: Montreal iTrader: (0) Garage List 2009 128i Coupe [0.00]	Weird noise when accelerator passes a certain point Had my 128 a week. Just today I noticed that when I push down my accelerator to a certain point, I hear a loud click (more of a KA-CHINK but not so metallic) come from under the car (it would seem, I'm driving so I dunno). Then when I bring the accelerator back up past this same point, I hear a similar noise (as if something first engaged and then disengaged, or sprung and then unsprung). Anyone have any idea what this could be? Doesn't do it when I'm in park (and not in gear). Tranny maybe? Someone else mentioned the engine mounts might need to be looked at? I'm calling BMW tomorrow and we'll see what they do, hopefully they know what the problem is and can fix it quickly. Manual transmission.. Last edited by supraking; 06-26-2009 at 12:08 AM..
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06-25-2009, 11:57 PM	#2
jeremyc74 Banned 76 Rep 5,970 Posts Drives: '08 135i Montego/Terra Join Date: Feb 2008 Location: Evansville, IN iTrader: (0)	Kickdown swich maybe? Does it happen to downshift about the same time you hear this noise?
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06-26-2009, 12:09 AM	#3
supraking Captain 49 Rep 759 Posts Drives: 128i Coupe 6MT Join Date: Apr 2009 Location: Montreal iTrader: (0) Garage List 2009 128i Coupe [0.00]	It's a manual (just added that to the original post).
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06-26-2009, 09:05 AM	#4
supraking Captain 49 Rep 759 Posts Drives: 128i Coupe 6MT Join Date: Apr 2009 Location: Montreal iTrader: (0) Garage List 2009 128i Coupe [0.00]	I just realized that it seems to be coming from the exhaust pipe. I looked into the pipe and saw a flap in there that I think is opening and closing when throttle reaches a certain point, I assume to eliminate back pressure? I saw a post about this a while ago, I'm gonna go try and find it. If anyone knows what I'm talking about please post a link.
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06-26-2009, 10:13 AM	#6
lib Major 141 Rep 1,401 Posts Drives: <This space for rent> Join Date: Apr 2008 Location: ATX iTrader: (0)	It's the flap in the exhaust that closes off one of the pipes. I began to notice the same sound a month or two ago and it's surprisingly loud now. When I took my car in for the first dealer oil change earlier this week I mentioned it to the SA along with another unrelated issue. At the time I didn't make a big deal about it but wanted to mention it in case it was something more serious. After they had some time to look at it my SA ordered a new muffler (the flap is apparently integral) and we're replacing the whole thing next week. If it happens again I'll probably do some version of the golf-tee mod to disable the flap.
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