What have you done to your XJ-S today (opinions welcome)

Just thinking out loud here and looking at another forum I think I need to ask the question.
I’ve hit the crossroads of my XJ-S.
I’m thinking I should replace the exhaust, either shift kit the transmission or yard it out and install a manual transmission , upgrade shocks and springs (which I’m in the process of doing) or respect the intentions of Jaguar engineering and keep the car as original as I can?
My back up plan is just buy a C4 Corvette ZR1 (yes I’m one of three people on the planet that likes them) bag drove it and sell it when I’m done?
My intent is to keep the XJ-S as long as I can.

Gary . . .
I think the long cold Alberta winter is leaving you too much time to think :grinning:.
However, I think your strategy ought to be to have 3 cars:

  1. a daily driver - something suitable for fetching groceries, car parts, and capable of carrying 4 or more people.
  2. a cruiser for sunny weekend trips with your significant other - a Jaguar XJ-S is the perfect example.
  3. a car you can take out on the back roads and drive it like you stole it - your Corvette idea for example.

Whatever you choose, best of luck.

From someone who has modified his 1988 XJ-S for better performance, here’s my opinion:

Over the last two years, I’ve removed mid-mufflers, opened up air intakes, put a simple shift kit into the TH400 for quicker shifts, advanced the timing a wee bit (4 degrees) and set the vacuum for the transmission so it downshifts with less throttle and upshifts at higher rpm. The car is MUCH faster and spirited that’s for sure…Night and day. I’ve also changed out the shocks with Bilstein all around, and put slightly lower profile tires on.

But the more I drive the car, the more I realize it’s not a racer and I just enjoy cruising around in it. Although it handles so much better with the Bilsteins, it will never corner like a Porsche. I am tempted next year to try OEM Sachs shocks just to get back that floaty ride. Yeah, I won’t corner as well, but I find myself not wanting to corner aggressively the more I drive it. I also can feel the road a bit too much with my Bilsteins, and maybe it’s not worth it.

But I will keep all the other performance upgrades, because they are on demand and I like the power and sound when I’m in a demanding mood :slight_smile: Yet I can still cruise quiet enough. The only real issue, I have to be a bit careful taking off from stops, especially in the rain, because the rear end can easily get squirrely now. And NO spirited driving on wet roads. I almost lost the rear end a month ago during a hard shift from 1st to 2nd at 60mph.

Since I can’t afford a 57-8 Rolls silver cloud (my dream car)… I have the Jag… I drive it respectfully… it isn’t a hot rod and I look at it as my luxury cruiser.

I think you’re right. I would like to respect the tradition of XJ-S Jaguar and not going down hot Rod road. If I can make it a little more snappy, produce a little more horsepower and a more throaty exhaust note I would suspect I would be a happy camper.
I suspect Jaguar started to think of older more select buyers with deeper pockets and decided to soften up the ride and smoother shifting (which was less than heart pounding). But you would have to think, all the fundamentals are there over square V-12, GM TH400 hundred transmission, and hey delete half those catalytic converters and you might be onto something without going all hot rod.

Oh how one thing leads into another - while searching for my engine number (finally found number 8S80864SA), I found a lot of oil crud on the back top of the “V”, all over the oil pressure sendor switch, and below the “B” bank valve cover - I figured blocked PCV valve, located on “B” air filter housing - ordered new one and installed it, since I found it was definetly clogged and not operating - removed the bulbous hose covering the crankcase breather screen, located at the front of the “B” head, and found the mesh screen unit very dirty with lumps of oil crud - no success in removing the mesh screen unit since it was very stuck in position in the housing - tried 3/8" (too small) and 7/16" (too large) spanner on housing bolts so posted question on “V12” section for thoughts of spanner size - was advised to try 10mm (did not know metric size was used on my 1991 XJS V12 Coupe) so will try that tomorrow, since have sprayed PB Blaster rust penetrant liquid to allow soaking overnight - sent 2/19/2021 2045hrs. EST USA.

When faced with the decision of being a bit more performance oriented or a bit more comfort oriented, Jaguar always leaned towards more comfort. But these cars respond well to simple tweaks and mods. You can tip the scales towards a more performance/sports flavor without making the car brutish.

The 400 trans/2.88 final drive blunts performance quite a bit but, still, a few tricks will liven things up.



Could be two problems.

I found a lot of oil at back of Vee, was simply a bad oil pressure gauge sender. The one with the big rubber cap on it. Very common to leak.

Your PCV clogged is def not good, once replaced and mesh clean, i would run some MMO in the oil and change frequently every three months to help clean out the engine. Without a well functioning PCV system, sludge will build up.

As you wish, of course. But, these cars are not made out of glass :slight_smile:


Terrific choice and, as performance cars go, undervalued. (C4s in general and ZR1s in particular). I’d love to own one


Hello Greg - yes, I am going to check the oil pressure gauge sender also, thanks - what is “MMO” that you are recommending to run in the oil - agree that the PCV system needs to be kept clean through regular maintenance - don’t think mine has been touched in a while by previous owner(s) - sent 2/19/2021 2310hrs. EST USA.

Marvel mystery oil. IMO its a decent non-solvent additive that can help clean sludge slowly but safely. Changing oil/filter every three months because the filter will collect a lot of the sludge.

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Hello Greg - will look at auto parts store for this cleaner - here is a couple of photos of my crankcase breather mesh screen and the bulbous cap - both very dirty

- sent 2/20/2021 0026hrs. EST USA.

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Hello Greg - meant to include photos of dirty PCV valve also in last message, so here they are now (just to show how dirty it was)

- sent 2/20/2021 0032hrs. EST USA

Wow, yep, that needs changing. How long did you run like that? I hope internal sludge isn’t too bad.

With a working PCV system, you may notice change in idle, a bit higher. So you may have to adjust idle rpm.

I do not know how long the car has been run, since the PCV valve, and the crankcase breather mesh screen, were attended to - I have only drove the car about 20 miles, and maybe ran the engine about 5 hours total, since I acquired the car in October 2019 (all due to health problems not being able to work on the car) - yes I was not happy to see the oil crud build up - sent 2/2021 1102hrs. EST USA.
Edit - my warm idle has been around 550 rpms.

I agree with Ron on the XJS issue. I have a 1992 model, and it has no brakes, so it gets started occasionally and sits in the building. Brakes in '92 were electro-hydraulic nightmares and need a vacuum booster retrofit to make the car stop. Why Jaguar does things this way is a mystery, and I was told about $3000 would fix the problem. For what it is, it’s a good-looking car in red with a bisquit interior. It is NOT a replacement for the E-type, but they stubbornly built it for nearly 20 yeas. Some folks love them. When it warms up, I will give it my best shot, make it stop and sell it to some poor devil and share the pain.

I think you’re on the right path, I removed my PCV , rubber boot, pipe and housing.
My screen for the PCV would not come loose. The rubber elbow boot can get cracked with age.
But once I removed it all (about an hour job to take off and put back together) I just soaked it all in a good solvent for an hour or two. It cleaned right up.
Buy a new gasket for the housing and smear on some Hylomer Blue (no affiliation).
If you look at the video , Living With a Classic Jaguar , PCV Valve , Adam has a great video and walks you right through the job.
For some reason this simple maintenance task gets over looked and can save you a lot of leak issues as well.

Yep - saw the video, but his screen came out nice - I am in the process now of removing the housing bolts (one out, the other not yet so re-soaked) - will be soaking housing and screen to clean (as you suggested) - sent 2/20/2021 1337hrs. EST USA.

Marvel Mystery Oil