So I've been working slowly through maintenance and repair issues on the '88 xjsc I bought a month ago and posted a pic of. I've been driving the car regularly, and have a bit of a stumble/misfire at idle, and I would say performance is OK, but lackluster. I didn't know what I should expecting, though.
Yesterday, I started removing all of the obstacles to plug removal, including the capstan, cruise control, and A/C compressor.

After spending some time cleaning 31 years of crud out of the vee, I started looking into plugs, especially curious about whether the hard-to-get-to ones had been touched. I reached for the plug wire on the driver's side of the A/C compressor, and found the wire loose, and only resting on the tip of the plug. I thought "cool, a smoking gun for my miss..."

Then, I reached for the plug. It was so loose in the threads that it pretty much just fell out. It was possibly in contact with a thread or two. It had what looked like years of blow-by residue coating the sides of it.

I guess I have been driving a V11... Amazingly, it ran remarkably well. can't wait to try all 12.

 

Yours is not a particularly unusual story. These engines will run 'fairly well' even with some rather glaring faults.

I am 100% sure that many of these old V12s are not running up to par and the owners don't even realize it. Dirty throttle bodies, worn and mis-adjusted throttles, inoperative vacuum and centrifugal advance systems, worn spark plugs....

Cheers
DD

 

When I purchased my XJS I stumbled across my distributor cap completely cracked in half with one side half fallen off the dizzy base plate.

it still ran perfectly fine on all 12 pots.

i was flabbergasted and simply replaced it.

cant believe she ran ok like that