Diagnostic OBD socket +stalling problems when cold (AJ6)

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I've got a DB7 (93-95 XJS platform)and was wondering if the diagnostic socket is the same?
Just curious if any of the similar powered Jaguars have a round black OBD socket with 4 wires?

Has anyone had a wee problem with thir engine stalling when cold?
Engine seems to 'hunt' at idle and is only kept alive with the throttle pedal. Car runs fine when warm. Revs are usually about 6-700rpm when cold but now it tries to stay alive at 400 revs. Engine warning light is on.

Just curious if anyone has encountered this problem?