A year ago I drove my always reliable daily driver '88 XJS home to my garage. A couple of weeks later I tried to start it and it ran extremely rough, as if it was running on half the engine, so I shut it down. Mine has the Lucas solid state ignition module. Since then it has sat under cover until I had time to diagnose the issue and get it back on the road.
Now, a year later I'm back on the effort to get it running again. I did buy a new distributor cap and rotor at the suggestion of some of you on this forum. So what sequence has to be followed to even get to the distributor cap and rotor that appears to be down in the bowels of hell? Thanks!

 

Oh boy.

Your market covered that sucker well from what I hear, we had almost nothing above that cap.

When removing pipes, hoses, etc, take snaps, draw mud maps, whatever YOU need to remember. LABEL everything as you go.

Mostly, removing the cruise bellows assembly, will open up things more than it appears,

Remove the coil, and when its out, look at the bracket, and SLOT the holes, so the bolts only need to be backed off a couple of turns, and the coil assembly can be lifted out, 30seconds next time.

It looks worse than it is.
That #1 requirement I mention often to owners of the V12, "you need a very warped sense of humour, then all will be well" is now at play.

 

Coffee went cold, priorities changed.

I would be seriously changing thf HT leads, all 13 of them, AND the 12 spark plugs.

II always run NGK BPR6EF, that "P" has the actual spark out in the Bang Juice, as apposed to the "normal" plug that have the spark partially shielded inside the cone. You car, your call.

Then that infamous Injector Loom is poking its head up as past its use by date.

 

Thanks Grant. I'm definitely one to take detailed pix and notes on this car in the past. The last time I worked on it is when I removed the steering column to run with a wire up the center so the horn now works properly. I also removed the speed control bellows at the time to repair it, so I remember looking down deep in the valley hoping that I wouldn't have to deal with all that crap. Now I have to "bite the bullet". I just don't want to remove more than I have to to get the rotor and cap out.

 

I was thinking about some things that happened to in Jag just prior to the extreme rough idling. It ran very smooth before sitting for a couple of weeks. I'd like to share this sequence of events with the group for comments.
1. About a month before the rough idle problem I drove it to work and when I "floored" the accelerator it locked up the linkage full speed/RPM. I managed to get around the block with me standing on the brakes to just get it back home, since pretty Jags parked on the roadside look bad. It was a scary experience with brakes smoking.
2. Examining the linkage I could see the plastic linkage bushings were cracked on each throttle side and "hung up in a bind" I pulled it out of the bind, started it again and it idled smoothly.
3. I drove it to work, vowing not to go full throttle again until my new throttle bushings arrived. All was well for about a week of daily driving.
4. The car then sat un-driven for several weeks after the 2 plastic bushings arrived.
5. When I started the car to put it in my workshop is when it ran rough enough to make me think half the engine was dead. At that point is when I parked it (under cover) since last Fall.

Last night I Looked again at my linkage on both sides and see that there is now no plastic throttle bushings on either side of the engine. Its all gone. The linkage is all "floppy loose".

This is obviously part of my problem, perhaps THE problem.

Does anyone here know the proper way to install these plastic (rubber?) bushings without ruining them. .

 

You can drop them into very hot water to soften them up, of FAR better fit a couple of these:
https://www.ebay.co.uk/itm/324493998...Bk9SR_rsm7qyYg

 

Greg's method is more humane than mine, so go with that.

Those missing bushes will have NO strange events at idle, NONE whatsoever.

BUT

Once off idle, look out, the brown stuff will hit the fan hard.

Remember, I say it hundreds of times, that engine is a Double Six, think about that every time you work on it, and if the "balance" is out, it will always be a dog.

 

I like those teflon bushings. The ebay listing pictures shows 2 bushings (a pair).. I need one for each side for my car so is the listing for a pair (one for each side) or do I have to buy 2 individual bushings each at that listing (twice the $).

 

The listing is for a pair.

 

Well not to try to throw water on the party it might be something else. Given the age of the car and that it has sat for awhile it might be clogged or restricted fuel injectors. It might be time to go deeper than just a hose replacement and distributor shaft lubrication.
Fuel injection refurbishment can either be outsourced (about $525 plus shipping) or self done with time and patience.
new FI filter, cap, 'O' ring, hose, and ferrules if needed. Pressure/spray test prior to installation.

Another thought is that you might have had a mouse nibble away on a wire or two creating a minor short preventing optimum running.

Finally, I strongly recommend going to Magnecor 8mm plug wires. Yyears ago I witnessed the OEM 7mm wires in a dark garage. The 'Vee' looked liked the aurora bourialis. Not a pretty picture when you consider all the fuel in close proximity to the cap and wires. Dreaded engine fire. Once I replaced the wires on the advice of Doug and others here all of the arc'ing completely disappeared.