Hi all,
I've been working through all of the maintenance and tuning issues on my 88 xj-sc that I bought 2 months ago. The car is in excellent condition with 27,000 miles, but like many, suffers from nearly 16 years of sitting idle, and some misguided maintenance as well.
I've changed plugs, wires, cap and rotor, repaired sensor connections etc. Also did the basics on the throttle side; TPS, linkage bushings, etc.

Here's my main question:
Using the "advance and test drive" method to get to an optimum timing position, and have advanced the distributor until the cam-driven adjustment has run out of range. Probably have advanced it in the neighborhood of 8-10 degrees, although that's just a guess. The car is running far better, although still feels a tad underpowered, and still has a slightly rough idle that may or may not be related to this. There is no pinging, or even a hint that I've gone too far. Have access to, and use 93 octane fuel here in Minnesota.

Is it likely that the entire distributor needs to be rotated a little to provide more adjustment range? Is that done via the slotted adjustment with the Allen bolts that is just below the distributor base?

Also wondering if this is a sign that I'm not getting the centrifugal or vacuum advance that I should be. The rotor will snap back reasonably well when turned by hand, but the range seems pretty limited based on where it sits in the slots on the clear plastic dust cover.

Appreciate any input!

Thanks,
Chris

 

Assming Lucas ignition? then Yes, rotate the thing a touch, clockwise.

As for the automatic advance, remember that with 12 poles on the dizzy, the advance cannot be very much or the rotor gets to the next pole!

 

Great. Thanks for the fast response, Greg. I'll be conservative. Fun to see the improvements as I get everything sorted. It's remarkably sensitive to ALL of the little things being right...

Best,
Chris

 

Well done, another clever V12 owner, you will go far.

Maybe this needs a "tickle" also, to smooth out that rough idle.

 

I doubt it. Not unless you have reason to believe the distributor has been removed or tampered with previously. Very few have, I suspect


Failure of the vacuum capsule is somewhat common. Use lung power on the vacuum hose. You should be able so observe the 'pull' on the advance plate.....distributor cap removed, of course

Also, Jaguar used a really complicated vacuum advance control system. It's plausible that one or more of the components are the blink. many ditch the whole mess and run a vac hose right to the unused spigot beneath the RH throttle body.

(Or is it above the RH throttle body? Gah ! Someone will clarify I've had a long day )

Cheers
DD

 

Good work. You've already covered a lot of ground.

Cheers
DD

 

COFFEE Doug.

That spigot is under the RH throttle body and the "inboard" of the 2, if your market has 2.

 

Thanks for the input all. Will get into that this weekend. Next weekend is steering rack bushings.......