My engine lite keeps coming on. I have had previous cars that have also had the engine lite come on and it was found that it was the result of the fuel cap not being properly fitted. When my 04 XJ8 comes on I fiddle with the fuel cap and it seems to eventually clear the engine lite. I notice in the after market sites that a fuel cap is one of the few items available. Is this an indication that the quarter turn cap has inherent problems affecting the emission controls? I also notice seat belts was another item readily available and mine is showing abnormal wear. Anyone ever replaced a front seat belt and is it fairly easy? Any and all help would be appreciated.

Bill