Originally posted by doctorsohc
I would check engine compression - if you have one cylinder that isn't doing the same work as the others, you will get some vibration - if all the cylinders are within 15 percent of each other, then I would suspect a broken piston skirt or a bent connecting rod - could also be the torque converter in your tranny. If I'm not mistaken your accord engine has a balance shaft in it, which could be out of time as well causing vibration. All this is assuming that you've already tuned up the engine (plugs,wires, cap rotor, etc.) I would also check your egr valve, it might be stuck open - CEL ?
I don't think it's internal because the vibration goes away right off idle. I would think an internal balance problem would increase with RPM. I have done the full tune-up and replaced the all motor mounts except the rear, which I still think may be the issue. I've just never seen a vacuum controlled motor mount. Thanks.