Vibration at 2K rpms with AC on.....
Thread Starter
Burning Brakes
Joined: Apr 2003
Posts: 788
Likes: 15
From: Martinsville, Indiana
Vibration at 2K rpms with AC on.....
I have a 94 AB coupe with an auto and just had EM longtubes and Corsa cat-back put on. The mufflers where they hook onto the intermediate pipe are loose because the clamps are worn from the previous owner. I've tried to tighten them but when I get back from a drive the right side tips are crooked. My problem is that right at 2K rpms with the AC on in any gear, I get a vibration through the floorboard and shifter. It only happens at that rpm and does not happen with the AC off. Could it be that with the loose exhaust in the back and the extra load on the engine the muffler is vibrating against the body or do I need to worry about something else? Again it only happens with the AC on right at 2K rpms. Thanks! 
Mark
Mark
Last edited by Indiana Z06; Aug 8, 2006 at 12:54 AM.
Melting Slicks
Joined: Jun 1999
Posts: 2,872
Likes: 3
From: Wilmington NC
I am betting when they installed the long tubes they did not reinstall the support brackets on the back of the alternator and AC. unless EM supplied stand offs and hardware, those brackets eliminate the vibration you are describing. I was able to get rid of it by reinstalling 1 of them, and I had the same vibration.. not good for the bearings in the alt at all by the way!
Chris
Chris
Le Mans Master
Joined: Aug 2004
Posts: 5,141
Likes: 7
From: Metairie Louisiana
I am having the same issue. I have not solved it yet. It looks like it's an ac bracket issue. I will try to talk to the installer today to see what can be done. See the thread I started on this below.
http://forums.corvetteforum.com/show...sted=1#post155
Thanks
http://forums.corvetteforum.com/show...sted=1#post155
Thanks
Racer
Joined: May 2003
Posts: 304
Likes: 1
From: beaverton oregon
I'm having this exact problem. em longtubes, missing brackets, vibration over 2000 RPM.I am actually glad to hear other folks having this problem. I was getting ready to replace the compressor...
Melting Slicks
Joined: Jun 1999
Posts: 2,872
Likes: 3
From: Wilmington NC
the one that goes to the AC botom rear bolt.. if you can get the other that goes between the back stamped brackets and the same header, it will solve the problems.. the other one will absolutely NOT fit with long tubes at least not the hooker 2149 or 2151 long tubes. if you have a chop saw, a bi vise and some steel stock you can get creative and make some new supports which will also help cure the problem.
Chris
Chris
Le Mans Master
Joined: May 2005
Posts: 7,319
Likes: 2,239
From: Central Maryland
I have a similar vibration only with the A/C on. I haven't tried to chase it down yet, but will do so soon (I don't use the A/C much, as my car's a ragtop).
This sort of vibration might not always be attributable to bracketry issues when headers are installed, as my LT1 still wears its stock manifolds. I'd be interested to know if other LTX owners are having a similar vibration with stock manifolds...
Be well,
SJW
This sort of vibration might not always be attributable to bracketry issues when headers are installed, as my LT1 still wears its stock manifolds. I'd be interested to know if other LTX owners are having a similar vibration with stock manifolds...
Be well,
SJW
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Melting Slicks
Joined: Mar 2003
Posts: 2,472
Likes: 0
From: Toronto ONTARIO
Chris can you explain in a bit more detail the bracket you are talking about ? Reason i ask is i just found out about these other supports down there and put one on that goes from the middle of that tri-brace (black metal bracket that atatches to athe alt, ac and manifold) to a header bolt down below. if there is another bracket that can be installed it would make me feel much better.
