This is a good opportunity to reiterate that every XJ40 owner should have in their emergency kit, preferably in the boot (trunk) of their car, a new rotor and a new, or at least known good, crankshaft position sensor (CPS), as those two parts can fail and leave you stranded. How do I know?
My '94 Died At a Stoplight and Wouldn't Restart?
Both parts are easily field installable, the rotor with no tools required; the CPS requires an Allen (hex) wrench that should be in the at-least-minimalist tool kit carried in the boot. A new distributor cap should also be part of the kit, to go along with the rotor.