something has been thumping the floor of my car from underneath, frequency stays totally in synch with the speed, not necessarily the revs, if i touch the floor on the exhaust bump right up next to the center console it feels like its hitting right there
crawled under it, found nothing out of place
is the exhaust pipe bumping up against he floor?
Check it from the top; there may be something there. You can’t tell if your engine mounts are bad without a little experience.
This is a way to look for things in general and maybe an engine mount problem will show up. With manual transmission in fourth gear rock the car and look back there. If automatic, put in park. Do this on level ground to prevent a potential disaster.
When this fails to reveal anything, see a mechanic.