I just resently bought a 1993 jaguar xjs 4.0 that had been sitting for months. The previous owner didn't have alot of information about maintenance, but he did do some work on it. When I start my jaguar, when cold (under 32 degrees) the engine starts but runs very rough and searches for a steady idle for about the first 5 minutes, until the engine warms up.
I've replaced the temp. sensor, removed and cleaned the throttle body and the idle control valve. The idle control valve does seem to operate, although I can't say if correctly.
Is there any sensors or control that acts as a choke on this jag. that I can check or replace.
I am not reading any codes at all and when the car warms up, it runs fairly smooth and idles steady.
The car did sit for months without being driven by the previous owner and the gas may not be the best, but I don't know how that would effect it when only cold. I did add some gas additive with plans on driving it to clean the system out, but the rear brakes went out, so the best I can do is start it in the garage and let it warm up to idle.
At this point, I'm at a loss for ideas and any suggestions would be greatly appreciated.

 

How about checking / cleaning the Auxiliary Air Valve (AAV)? The AAV sort of acts as a choke, varying the air flow with temp.

Whoops... Sorry, the brain just kicked in. Just realized you have the 4.0, not the 5.3 V12. I doubt the 4.0 even has an AAV. Someone with 4.0 experience will have to chime in.

 

See if you can find a couple of ground lugs on an intake manifold near the front, right behind the thermostat housing. I seem to remember a problem like that if one of them break a wire off or are left disconnected.
Just a thought.

Cheers,