I was able to duplicate my vibration problem that I've been having out on the interstate tonight in the driveway with the engine reving to the same RPM as cruise RPM - about 1500-2000. When I rev higher than that, the vibration decreases and almost goes away. If the vibration was caused by the clutch or flywheel, wouldn't it get worse with RPM? Think this could be a slight misfire problem and not a flywheel/clutch/engine balance issue? If my car still has the factory dual mass flywheel, is this normal?

 

OK, I'll simplify my question:

If the clutch, flywheel or engine is out of balance, would the vibration definitely get worse as RPMs climb?

 

No.. Harmonics come into play, just like a bad balance on a tire, there is a speed where it is really bad and it gets better above and below that 'sweet spot'.. All objects have a resonate frequency and any vibration will be substantially more pronounced at that frequency..

You're probably on track with the clutch assembly being at issue. If it is severe enough to blur things in your mirrors etc, you may have lost a mounting bolt for the pressure plate. If it only does it with the clutch engaged but not when the pedal is pressing it, then you probably have a bad pilot bearing which allows the clutch disk to be clamped off center.

 

I noticed no difference between the clutch out or in. I'll be doing some more investigation and post what I find. I'm leaning now towards a slight misfire now, especially since occasionally the engine will miss when when I stomp on it. Since the new Optispark I put in only about 20K miles ago has had hot coolant on it, I should probably swap it back out and see what happens. I've already changed everything else out ignition-wise plus put on a new fuel pump. Even though the Opti isn't cheap or easy, it's cheaper and easier than a clutch replacement, so I'm starting there.

 

I spent the better part of a day installing the new Optispark and no change. I do have loose hubs front and rear on the passenger side. In other words, I can feel some play when I wiggle the wheel with it up in the air. The ones on the drivers side are tight. Could this cause very much vibration?

 

Similar problem with running gear vibration. GM agreed to a one time courtesy fix. Aren't they just wonderful? They replaced the clutch, pressure plate and bearings. It is a little better but I still have the slight clutch chatter as I let the clutch out very slowly in first gear. I will just have to live with it. I have had other problems with the car but can't afford to sell it for awhile.

I have a 2014 base model with 8000 miles and M7 transmission. It took the "specialist" over a week to finishing the job.

 

Yes I sure would be fixing it.

 

I agree with antfarmer2 that you should fix the hubs and that they can cause vibrations, etc.

However that is not your vibration problem if you can duplicate the vibration in your driveway when the hubs have no rotation.

Good luck.

 

If you can duplicate your issue in the driveway (not moving) then it is not a driveline or whee/tire issue and therefore not a hub issue either.

If you can duplicate the issue in the driveway and it does not matter if the clutch is engaged or disengaged then it is not a transmission issue or a clutch friction issue.

Since you have changed the OPTI and still have the exact same issue then you can assume it is not an OPTI issue. That is all you can assume though.

I would say you have a rotating mass imbalance issue or a combustion imbalance (misfire or no fire) issue.

What would cause these problems?

My guesses are (in no particular order)
1. Harmonic balancer worn
2. Flywheel imbalance
3. Timing chain worn
4. Crankshaft imbalance
5. Low compression on one or more cylinders
6. Worn or faulty spark plug wire
7. Worn or faulty spark plug
8. Leaky head gasket
9. faulty or misfiring injector(s)
10. worn or imbalanced accessory drive (A/C, power steering, etc.)

You really gave us very little to go off of to assist in troubleshooting.

Does the engine RPM fluctuate or surge when the vibration occurs?

Does turning the A/C on/off influence the vibration?

Have you done any other maintenance to the car just before the issue came up?

It could be a bad motor mount as well but chances are slim for that given your explanation of the situation.

 

When my flywheel was asked to be transfer balanced (after single mass failed), it got really bad vibration with rpms climbing. A cup the size of a big gulp full of water walked across the targa top. I only think I took it to 3000-3500 rpms and then began removing the engine again.

How is the harmonic balancer?

Is it running rough or out of balance.
Huge difference!

 

Everyone has very good suggestions. In addition I would suggest checking the motor mounts. If they're going bad they could be allowing engine movement at certain rpm ranges that may feel like a vibration caused by a miss or bad part.