Hi. My '02 XJ8 3.2 passed its annual MOT (roadworthiness inspection) this week with no advisories. Hoorah! However, the tester did tell me that the emissions check was only passed once he swapped the probe from one tailpipe (n/s - left) to the other (o/s - right). The first one was a clear fail whilst the other was an easy pass.
As the exhausts from the cats come together and mix gases in the first silencer I'm really puzzled why this should be.The vehicle is running smoothly with fresh oil and filter, although the gas mileage is perhaps a little lower than usual at the moment (25mpg on recent, steady 70mph cruise over 450 miles). No fault codes are showing though.
Anyone got any ideas what's going on?