I just swapped an f23 into my 95 accord wagon ex. Before putting it in I did timing and balancer belts. Water pump and pulleys. Got it all into the car, (I reused my intake manifold with a new gasket) and car seems to run fine, even idles down to about 750 rpm with no phantom revving. I replaced front and rear motor mounts while the car was out. However I seem to have a really bad vibration while the car is sitting still (both in drive and park). How do I go about isolating this? It does not look like the engine is shaking furiously.

 

Just a few guesses, based on nothing but my own frustrations with the same thing.

1 - Did you use aftermarket motor mounts? I ask because as far as I can tell, all the aftermarket motor mounts are too firm and will cause the vibration. I'm not sure why, but I guess the rubber compound is just too firm. I had this happen on our camry, accord, and civic. You could get away with maybe one aftermarket, but for total smoothness I had to switch them to OEM mounts to get the vibration to go away. It sucked because the OEM is so much more expenseive (I think I paid like $50 for aftermarket, $250 for OEM for example), but it was worth it to get rid of the vibration.

2 - Motor mount overtightened? I had this happen on the Accord. I installed the new motor, cranked everything down, and it vibrated while in gear but my foot on the brake. Going around and slowly backing off on some of the motor mount bolts showed me I had one that I either had crooked or too tight. Remounting it again and tightening to the point before the vibration got rid of the issue. In my case it was a side mount causing most of it, and the front mount slightly causing it. Again, just loosening and retightening it seemed to help it settle into place and stop the vibration.

That's my guess of the morning.

 

I used after market front and rear. The side mounts weren't torn so I didn't bother with them..

 

Yeah, I tried aftermarket rear, and it was terrible. Huge vibration. Switched to the OEM with the vacuum and it was like night and day.

Again, you could try loosening to see if it helps.