Hello, I have a 2003 automatic SE with an unknown issue that I've been trying to solve for the longest. The car vibrates when I put it in drive, while simultaneously making a noise you'd probably associate with an old pickup truck. I've looked everywhere for answers and videos, but just couldn't find anything on this particular matter.

Since this phenomenon started, my fuel economy and performance had taken a dive, so perhaps that rolls out the engine mounts?

Here's a video

Also, I'm pushing 250k miles.

 

I think that maybe you are running on 5 cylinders instead of 6. When the engine is idling, unplug the ignition coils one at a time. If the engine idle slows down and shakes when you unplug a connector, that cylinder is working. If there is no change, then that cylinder is not working. A not working cylinder is either a bad ignition coil or fuel injector. Swap ignition coils with another cylinder and retest. If the problem moves with the ignition coil, the coil is bad. If the problem stays with the cylinder, then the fuel injector is bad.