Bad engine vibration...new mounts made it worse??

87lc2

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Oct 16, 2005
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I replaced the balancer about a month ago and that helped a bit, but i also noticed the factory mounts were trash. Replaced them with Prothane mounts today and the vibration is now [email protected]! the whole console shakes when driving. Its between 1000 and 3000 rpm at its worse. happens both while driving and while in neutral and reving. Any advice on where to start would be greatly appreciated.
 
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HISSIN50

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Nov 29, 1999
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Try running a cylinder balance test. The source of the vibration might be a miss, which indeed will be transferred to the body more easily with the new mounts.



Good luck.
 

87lc2

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Oct 16, 2005
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thanks guys, heres where i am now...I pulled the plugs and they were all a bit white, so i checked the timing and the previous owner had it at about 13 BTDC, so i put it back to the factory 10 becaus ei run regular gas. I then did a vacuum check and a compression check, all were even and vacuum was good. I do have an exhaust leak where the headers meet the h pipe, coudl this cause a vibration with the poly mounts? I drove it tonight and it is right between 1300rpm and 1900 rpm, anything lower or higher its hardly noticeable. HISSIN50, by a balance check you do mean compression check right? with this new info, does anyone have a better idea of where to check?
 

HISSIN50

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87lc2 said:
HISSIN50, by a balance check you do mean compression check right? with this new info, does anyone have a better idea of where to check?
Nope. You let the computer do the work for you. The procedure is in the repair manual (I think you have to goose the throttle within 2 mins after pulling KOER codes, but check that). It systematically drops injector pulse to each cylinder and notes RPM drop (ergo contribution). It can use varying criteria/thresholds to narrow things down.

Jrichker has a nice write-up on the CBT.

Good luck.
 

grey5.0beast

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Aug 3, 2004
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are you overheating at all? I had a horrible, I mean HORRIBLE vibration and it ended up being a bad fanclutch and water pump.
 

Daggar

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Jul 19, 2004
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check to see if any part of the motor is touching any part of the car that it's not supposed to be touching. You should also check the transmission to ensure that it is not bound up or touching anything that it should not be touching.

There are probably 100+ different points that can transfer engine vibration to the car. Prothane mounts were def a set in the opposite direction. I doubt that I would use those on anything other than an internally zero balanced rotating assembly.
 

87lc2

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Oct 16, 2005
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Finally fixed it!!! Thanks for all of the input guys, it turned out to be my 6 month old balancer. After doing the CBT and everything else suggested, i was at a dead end and decided to pull it. It looked ok, but i figured what the hell it has a lifetime warranty from autozone so i went and got a new one, and the car felt worlds better, but still not smooth. So then i went back to autozone and got the stock replacement convertible mounts and now the car is better than ever!!! i guess the balancer was bad for a little while and the prothane mounts magnified it. my last question is, sicne this thing failed within 6 months, is there a better replacement out there? or should i just keep getting new ones under warranty whenever i get the vibration again? anyways, thanks for the help and i figured id post back as i hate reading threads when searching and never getting a conclusion at the end...
 

HISSIN50

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For better balancers, Pioneer and Romac make good stuff. My most recent one was an SFI Pioneer - a nice piece.

A non SFI Pioneer suits most folks needs however (mine included. I got a deal).

Good luck.