I found this cable detached..dont know what is this for. I dont know if this is for my odometer/trip counter. My speedometer works though..anyone knows where is this connected to and from...thanks

 

Could it be the cruise control actuator?

 

That's exactly what it looks like. If it is it should run toward the front of the car (@ 90degrees to the throttle pedestal) and through a small bracket to connect to the bellows which nestle snuggly between the distributor cap and air conditioning compressor. I know that mid 80's XJS had an issue with cruise control getting stuck on (certainly in the UK), it was subject to a recall. I have the Jag paperwork relating to it for my 85 HE. A lot of people didn't fancy the risk and may have disconnected it in the meantime and providing the vacuum lines remained undistributed nothing serious would go wrong. I will try and get a pic tomorrow for you.

 

Here you go, sorry for the focus it was on my phone. Hope it helps!