Could a bad muffler even cause any KR? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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View Poll Results: Is it possible for a muffler to be "broken"?
Yes, its possible for a muffler to be broken and I can see it causing KR at the shifts 2 20.00%
Yes, its possible for a muffler to be broken but I DO NOT SEE how it would cause KR 2 20.00%
No, I dont see how a muffler can be "broken" causing any problems 6 60.00%
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Old 11-15-2006, 03:45 PM   #1
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Default Could a bad muffler even cause any KR?

My car clearly has an issue with KR, too much backpressure it seems, plenty of fuel, just at the 1-2 and 2-3 shifts it goes from 0 to 20*. So therefore I'd say it seems there is a lot of exhaust buildup when the RPMs go from 5300 or whatever to whatever it is after it shifts gears.


On startup and if reving, my muffler clearly makes a loud obvoius rattling noise, something is broken in there, but in my experience a muffler looks like this:




I assume the stock muffler on the ville'* is just like this.

I dont see how it would be possible for anything to be broken that would cause problems unless one of the pipes inside there is broken and rattling around.
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Old 11-15-2006, 07:59 PM   #2
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How bout your cat?

-edit: never mind, just read your sig...
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Old 11-15-2006, 08:09 PM   #3
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I really cant see how a muffler could cause real KR. I could see an exhaust rattling causing false KR though.

Any KR that jumps really high really quickly is usually false. Since you said that it is at the shifts I am almost certain it is false. Start looking for loose parts and exhaust leeks.
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Old 11-15-2006, 11:45 PM   #4
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Quote:
Originally Posted by PURENVY
I really cant see how a muffler could cause real KR. I could see an exhaust rattling causing false KR though.

Any KR that jumps really high really quickly is usually false. Since you said that it is at the shifts I am almost certain it is false. Start looking for loose parts and exhaust leeks.
I had the manfolds welded up. Extremely quiet in there now. there were leaks and cracks everywhere.


At 3500rpm shifts I still get 20 degrees of KR at times. Freakin weird.
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Old 11-16-2006, 07:48 AM   #5
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Not sure if that is what the muffler looks like on the inside. I'm going through a bit of muffler issues myself and have found that our mufflers are "unique" internally .
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Old 11-16-2006, 07:18 PM   #6
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Quote:
Originally Posted by Hans
Quote:
Originally Posted by PURENVY
I really cant see how a muffler could cause real KR. I could see an exhaust rattling causing false KR though.

Any KR that jumps really high really quickly is usually false. Since you said that it is at the shifts I am almost certain it is false. Start looking for loose parts and exhaust leeks.
I had the manfolds welded up. Extremely quiet in there now. there were leaks and cracks everywhere.


At 3500rpm shifts I still get 20 degrees of KR at times. Freakin weird.
Thats good to know that the manfolds are good. It is def. false or maybe torque mgmt. Something is causing it... It could be anything...

Few ?'*...

Do you get KR any other time? WOT?
Is the KR just when you shift at part throttle (3500RPM). Or on every shift?
When you get this KR what does your timing go to? Does it jump back quickly?
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Old 11-19-2006, 02:50 PM   #7
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Have you replaced the knock sensor itself? Over time, they tend to pick up false knock pretty easy because of how they are built internally.

The rattling could also be pieces of the old cat, or weld material that has come loose somehow.
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