I watched the engine for a while today. Can't find anything wrong. Motor mounts are fine. I used a flashlight and small mirror to look at all 4 of them very closely. Can't find any vacuum leaks. Don't see anything touching that would transmit vibrations. I listened to the injectors with a plastic pipe, and can hear them all clicking at the same speed and strength.
It sounds a little louder near the belts, and it's a throaty exhaust sound, but I can't find anything wrong with the exhaust other than a pinhole leak in the muffler that drips water. The hangers are fine.
Does this O2 sensor look right? This is a highway trip from about a month ago. I've got 4 charts from the trip.
Speed:
RPMs:
I think this is the O2 sensor up by the engine:
And I think this is the O2 sensor after the catalyst:
Shouldn't this second O2 sensor be pretty much flat? It's fluctuating almost as much as the first one.
There are no codes, and the check engine light is off.