I had just replaced the timing chain on my car about a week ago, that went fine. When driving to my parents for Christmas I noticed a small vibration when I would accelerate from 50+. I thought it might be snow on the wheels and didn't think much of it.
Yesterday I took it on a small trip the vibration started getting worse. It starts at about 54mph and it only present when you apply power. IF you let up on the gas it's gone. I can rock the engine at all, so the mounts seem fine. I jacked it up and the tires have no play in them. I am at a loss.. One thought though, when I had the top mount off, my jack lowered overnight putting a lot of stress on the other mounts.

Any ideas?

 

Any time there is a vibration like this I like to get to the problem speed range and go into neutral. Continued vibration at engine idol around 50+ mph means it isn't an engine problem but is likely tires or suspension. Helps narrow the issue which could be a simple alignment or balance

 

The vibration goes away when I put it in neutral or push in the clutch at speed.

 

is it in a specific gear when you're going 54+? I ask because if it's an engine problem the vibration would occur at a certain RPM no matter the gear, but if it is only in a certain gear like 3rd since you're going 54 it's probably a transmission problem. If it's neither of those I would say maybe clutch/flywheel imbalance.

 

I did more checking last night, and after my last trip, I now see a ton of play in the upper motor mount. unlike before, I can rock the engine back and forth., This has to be it

 

Get your tires check to see if a weight fell off, or if a band shifted. When vibrations like that happens and increases at higher speeds,and there's no grinding noise, its usually something that's out of balance. Your engine mount would show symptoms more at initial take off, and changing of gears since power is applied, gone, and reapplied.

 

Finally fixed it.. I replaced the lower mount even though it didn't look bad. I replaced it with a BSH lower. Once I had the old mount out, I stuck a screwdriver in the center and put pressure on the rubber bushing. It was torn in several places. Between the new upper and lower mount I am back on the road. I think the car even handles better with the BSH lower.

 

It's back.. Fine for 3 days, and now it's back! Only when I accelerate! When I let off the gas, it's smooth as can be. I hate this!

 

Does your steering wheel vibrate, or is it down by the pedals? I'm telling you, something is out of balance. Sinceit only does it at a certain speed, I'm putting my money on the drive train, like the trans, cv axles, tires, or even a bearing (though bearing a are more prone to showing it's vibrations at lower speeds) if it was engine related, it would sow the symptoms every time it gets to a certain rpm in each gear. Take a look and see if you see a shiny area on the inside of your rims, would most likely be a lost wheel weight, and go from there.

 

Double check torque on lug bolts.. if you missed the lower motor mount you May have also missed this.... Any lights on display? Code reader ? May have a code not being displayed. We can help you here if you answer the questions about certain RPM or speed only? Try gears 3,4,5,6. See if they all do it. You said it doesn't do in neutral but what if you're at 60ish. How bad is the vibration ? Is it in the wheel or the pedals. We need info to help ya....

 

It happens in any gear that I can exceed 50+ mph in. 3,4,5,6 etc. It only happens when I apply power. If I put the clutch in, it goes away. if I coast it goes away, if I put it in N it goes away.
Jacking the car up, I can grab a wheel and there is no noticeable play, vertically or horizontally.
I feel it in the pedals more than anything.. It isn't the engine, I can fly through the gears under full power and it runs great.
I searched on this for a couple hours last night and found a few similar problems like mine and it turned out to be the axle shafts, and or the support bearing on the passenger side. That is what I am starting to focus on.

 

Replace the rest of the engine mounts - one had gone - the others will be following.