Laurence, a comment on your ignition problem with your XJ-SC.
Now you can start and run it, a number of things to check that can cause it to misfire or run unevenly.

Check that your front coil is still working.
The best solution if you haven’t done it already, is remove both coils as if the front one is faulty it will interfere with the other coil, and replace with new single coil #DAC 6093, Ducelier coil – 0.62 ohms primary, that was fitted to the later V12’s.

The black throttle pot on the Jaguar V12 with Lucas Digital P EFI (1981-88 or so) is made by Bourns and is notoriously unreliable. The wiper wears through the resistive coating inside the pot and it starts “breaking up”. Fortunately, this doesn’t stop the car; in fact, many owners continue to drive for years. The car hesitates a bit on acceleration, but they put that down to normal aging or some such nonsense.

The pot is easy to check with a voltage meter; just make sure it provides a smooth resistance change from idle (0.32V) to full throttle (4.6V). If not, replace it.
Better replace it anyway, as the black pot will break down.

The later XJ-S’s came with a much better red throttle pot made by Lucas (!) that costs much less too!
A little bit of fiddling to fit, nothing too onerous.

• This reply was modified 4 weeks ago by Laurence Jones.
• This reply was modified 4 weeks ago by Laurence Jones.

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