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Discussion Starter #1
:) Gentlemen

I know it’s not a Mustang but still the same engine. I am working on my sons 1994 Cougar XR7 3.8 V6. It has about 35,000 miles on a dealer installed remanufactured engine. This engine just started to vibrate badly from just over idle to about 1,500 rpms, after that the vibration disappears. It starts well and runs strong without missing. It vibrates at this rpm whether on the road or if I brake torque it in the driveway. I suspect the harmonic balancer has failed, as it is the original from the first engine that was in the car. That engine had 120,000 miles on it before the head gasket failed. Is this usually what happens when a vibration dampener fails? I have never had one fail before. Thanks!
 

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Mine went bad and the motor pretty much responded the way you are describing.
If you can get under the car you may be able to see if it's coming apart or it may have rubber sticking out of it. Either one is a bad sign.
 
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Stone Cold is right. Mine balancer had a really bad wobble at idle speed. You could see it no problems. My engine vibrated like you are describing too.
 

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Thanks guys, before spending $146.00 for a new one I just wanted to make sure I was on the right track.:wavey
 

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Zephyr said:
:) Gentlemen

I know it’s not a Mustang but still the same engine. I am working on my sons 1994 Cougar XR7 3.8 V6. It has about 35,000 miles on a dealer installed remanufactured engine. This engine just started to vibrate badly from just over idle to about 1,500 rpms, after that the vibration disappears. It starts well and runs strong without missing. It vibrates at this rpm whether on the road or if I brake torque it in the driveway. I suspect the harmonic balancer has failed, as it is the original from the first engine that was in the car. That engine had 120,000 miles on it before the head gasket failed. Is this usually what happens when a vibration dampener fails? I have never had one fail before. Thanks!
It could also be a cross-firing plug wire, a dirty MAF, a bad injector (clears up as pressure increases), or a bad motor/transmission mount.
 

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It's smooth again!!!!

Update, removed the old harmonic balancer in two pieces! The end that rides inside the seal was broken about two inches from the end. The woodruff key had sheared the keyway in the balancer. When I saw the keyway damage in the balancer my first thought was “Oh God, let the crankshaft be ok”:worship Lucky for me it was! Installed a new oil seal, key and balancer. Not only did the new harmonic balancer stop the vibration, the engine idles and runs smoother than it ever did. I will check the timing tomorrow with a timing light to make sure it’s right on. Unfortunately this engine has the old distributor ignition system. Thanks you all for your comments!!!

:wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey :wavey
 

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Good to hear it was the balancer and nothing major, glad we could help. :smoke:
 

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STONECOLD said:
Good to hear it was the balancer and nothing major, glad we could help. :smoke:
Stoney get's the call!!

GLad to hear it!

:happyhapp
 
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