C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

87 Vibration during Acceleration

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Old Mar 5, 2008 | 09:57 PM
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Default 87 Vibration during Acceleration

Just looking for possible ideas on what could make a 1987 Corvette L98 Stock engine vibrate at 3000+ rpm. Thanks!
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Old Mar 6, 2008 | 12:31 AM
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Two things to consider.

A mechanical imbalance, or a tuning problem that feels like vibration.

So the engine vibs at only 3K? Or a range?
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Old Mar 6, 2008 | 05:37 PM
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Default 3000+

It shakes with the pedal to the floor anywhere over 2500 rpm most notably but not limited to second gear if that helps at all. There is also a slight vibration that can be felt at idling speeds but only if you are really feeling for it. This idle vibration can be felt in the seat of the car or in the steering wheel.
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Old Mar 6, 2008 | 05:46 PM
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check too make sure all of the pulleys are tight, also check the tensioner to make sure it's keeping good tension on the belt, check any brackets attached to the engine accessories as well, and give the motor mounts a check too.
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Old Mar 6, 2008 | 05:52 PM
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Remove your Serpentine belt in the drive way and rev it a few times, do yo feel the vibration? IF so, its a bolt on accessory.

I had a fuel pump issue that caused a vibration above 3200rpm once.
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Old Mar 7, 2008 | 12:51 AM
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Originally Posted by LD85
Remove your Serpentine belt in the drive way and rev it a few times, do yo feel the vibration? IF so, its a bolt on accessory.
Good suggestion, this will eliminate all the moving parts on the front of the engine. But the vibration at idle......

What have you already checked?
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Old Mar 17, 2008 | 11:55 AM
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Thanks for the input everyone. We have already tried balancing out the flywheel, but we could not feel any difference in the vibration at idle no matter where we put the weights at the 120 degree increments. This vibration at idle is actually a random pulse that happens at idle speeds all the time when it is in park, and can be felt at idle in gear.


PS. Just for clarification, the vibration above 3000 rpm would be a "shudder" actually that can only be felt in a short burst of time if that makes a difference to you.
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Old Mar 26, 2008 | 07:39 PM
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Default 87 Vibration

I removed the serpentine and unfortunately did not feel any noticeable difference in the vibration idle. Anything further?
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