I finally got around to replacing the O2 sensors because I used the XJ to take a load to the landfill and had the nasty heat soak issues again. So, after a little research and since I already owned the new O2 sensors, we finally got them replaced. Luckily they all came out without any fuss – not rusted in there at all.
Now we just have to test it out.
The vibrations are still there, however. It’s frustrating but we’re lost as to where to keep looking. It starts pretty low speed – probably in the 25-30 mph range and then just gets stronger as you increase in speed. I did determine that the speedo, when over 70mph, is probably about 5-6 mph off, but still, the symptoms remain. We pulled the front driveshaft again and tested it but no changes in the vibration.