Greetings! My 2004 XJR now has 116K miles and recently my front air shocks failed. As I was replacing them, I noticed that my suspension components (front and rear) were very worn so I replaced everything that looked bad. Now, after replacing the 4 original air shocks (rebuilding the air compressor) most of the suspension components, front and rear brake pads and rotors, tires, wheel balancing, and alignment, the car rides like new. I have loved the car since I bought it 7 years ago and this is the first serious maintenance (other than routine) that I've done since I really only drive it on bad weather days. The total cost of all my work (some labor but mostly parts) was about $3K which may sound like a lot but the car is in such great condition, that I felt replacing it with something as nice would be a lot more expensive and anyone who has an XJR of this era knows how great they are. I don't have any service records from the previous owner(s) so I really don't know the car's history but I will assume the plugs and coil packs are original so I'm thinking it's time to replace them too. So far, every job I've done was with the aid of DIY videos but I haven't found a single one to do the plugs. Is there any out there? I would appreciate any advice before starting this job. Thanks.

 

The plugs are straightforward except the one on each side right at the back.

Those are a fiddle.

I used a 3/8" square ratchet with two different extensions.

Have a flexible magnetic pick up tool on hand in case something drops into the cavity.

 

My father and I tried to do plugs and coils on my 2004 XJ8 VDP and the rear plugs and coils were completely inaccessible, even with extension tools. We went to our local import shop and their solution was to drop the engine in order to replace the coils and plugs. I think this stupid design flaw is the reason there's no videos on the job. If you find a way to replace the rear coils and plugs without damaging them or dropping the engine please let me know haha. Good luck.

 

Ugh, not good news. I can do a lot of things in my garage but dropping the motor to replace 1 hard to get to plug isn't one of them. So, is there anyone out there that has done it another way? Would love to hear from you.

 

2 years ago i replaced the sparkplugs on my 2007 xj8. The rear ones are a bit fiddly but with a small extension not too hard,, I would be very careful dealing with a garage that wants to drop the engine, not necessary in my opinion,

 

Dropping the engine is definitely not necessary! If a workshop wants to do this, stay away from them!

The divisions to the recesses left and right of the engine, where the pollen filter and the brake fluid reservoir are located, are plastic and can be removed to access the rear spark plugs. The job is fiddley, in any case.

The picture I found from when I did the job is not the best, but I hope that it shows a bit what I mean. At the back of the engine you can see that the divisions left and right are missing.

Best regards,

Thomas

 

I have a little over 130,000 miles on my 2005 Jaguar XJ8L. Personally, I wouldn't replace any spark plug or ignition coil on the Jaguar unless defective.

 

I agree on the ignition coils, but not on the spark plugs. These need to be replaced on a regular basis because they are "consumables", as the electrodes are subject to wear.
Normally, after replacement you should note improved performance and fuel consumption.

Jaguar recommends replacing the every 100,000 miles for the V8 engines, and every 70,000 miles for the V6.

Best regards,

Thomas

 

Thanks for all the helpful feedback. I just finished replacing both of the HID low beams which was a royal PITA. I did not remove the bumper so the room to work was very limited but all's well that ends well. I will be replacing the coil packs/spark plugs in the spring only because I'm worried that some unforeseen problem will prevent me from completing the job and since this is my only winter car, I won't risk it. Now for the oil change and I'm ready for the winter.

 

For the sparkplugs underneath the window there is a little trap to open you can reach through . And with different short and long extensions you should be able to get them out.
To the garage wanting to drop the engine ... do not go back to that place. They will change then like I wrote and ask the you to pay the big bill

 

With these aluminum block engines, I would likely spray some penetrating oil on the plugs, and allow that to soak overnight.

 

Huh? First, the plugs don't screw into the block. Second, aluminum heads have been around on various engines for 60+ years, so changing spark plugs in them is not a "new" thing.

 

Those spark plugs don't screw into the block? Gracious, that's a new one on me. As I had mentioned previously, for plugs that have been on an aluminum block for quite some time, I would never attempt to remove them without letting them soak in penetrating oil overnight. Actually, my brother tried removing a spark plug from a pickup truck aluminum block engine during the 1990s, and he ended up installing a helicoil.

 

I never had any problems removing a spark plug from any engine I have been working on.

Apart from this, you state that your brother had the problem in the 1990, and at that time spark plugs were usually quite unprotected from dirt, etc. Also, it might have been that someone had tightened the spark plug excessively.

If you look at the engine in our Jags, each spark plug is not only totally covered by the ignition coil that also has rubber seals to prevent the ingress of dirt and humidity, there is also the additional coil cover which gives some additional protection.

I do not see the need for penetrating oil, be it an aluminum head or not.

Best regards,

Thomas

 

DON'T spray anything in the spark plug wells!!
First always attempt to remove spark plugs with the engine as warm as possible. This will help.
Next BEFORE attempting any spark plug removal use compressed air and thoroughly blow out the plug well. Remember anything in there will fall directly into the cylinder when the plug is removed! Don't create more problems!

If oil is found you know the cam cover seals (Also called plug well seals) are leaking and you will need to repair that (Plan on that because of the age of the car. It's fairly common so not a sign of bigger issues.). I use paper towels to mop up the excess oil and also use paper towels around the compressed air gun to catch what blows out. IF it's bad then I spray carb cleaner in the plug well let sit a bit and then blow it out again. I do this multiple times depending on how bad the oil is. It can get very deep!

Please use the factory plugs and don't try to use "miracle" plugs that make all kinds of promises. The stock plugs are fine. As posted above Jaguar has a 100K miles replacement interval. All the plugs I have changed looked great and I noticed no difference in how the car drove. But again plugs are maintenance and should be changed before they cause problems.
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I would really like to get started on this job now but I only have a one-car garage that is tied up for the winter so it'll have to wait. I share my Jag "Jones" drive time between the F-Type and the XJR and until recently the F-Type was the go-to choice most of the time. But, after solving most of the annoying mechanical issues that made the XJR feel unexciting at times, I'm getting a feel of what it must have been like when it was new. So now, at 116K miles, I'm on a quest to get it even better which is why I'm doing the plugs and coil packs. Not sure if that's ever been done but it probably hasn't so maybe I'll get better gas mileage? Or even better performance? I'm just having fun with it and it's satisfying to "check off" all of the unknown maintenance items, it's an addiction of car guys. I hope everything I learn on this forum makes the job go as planned. Also, I'd like to add that I just replaced the HID (DS1) type low beams without taking off the bumper. It was a bit tricky working in a tight area but very doable.

 

On a reasonably warm, dry day, do them one at a time in the drive.
It is not a long drawn out job at all
The only two that will present any problem.
Is the back one on each side, but those arent really that hard to change.
With a couple of extensions & a swivel joint.
The oil fill spout unscrews to swing the ratchet

 

That sounds encouraging. To your knowledge does this hold true for the XJR as well as the XJ8?

 

Someone else will know better than me.
As i have not changed spark plugs in an XJR.
Start with the ones in front, & work your way back.

 

The oil fill spout is shorter on the supercharged engines and does not need to be removed. Apart from this, it should be the same, as the supercharger is located in the "V" of the engine.
You can see the oil fill cap of the supercharged engine in the following picture on the right of the engine:



Best regards,
Thomas