Hey everyone, I've got an issue with my XJS (v-12) that i'm hoping someone can help me with. The last time I drove it, about two weeks ago, It bogged down while I was driving and the RPM gauge went to zero. I pulled over and rev'd the engine a couple of times. It sounded like it was backfiring a little in the muffler and after about a minute, it jumped right back to normal and the RPMs started showing again. I put it in the garage and haven't run it since. Yesterday, I went to run it and it did the same thing. With the hood up, I rev'd it up again while it was bogged down and figured out that its something in the right bank. It is only backfiring from the right side of the exhaust and you can hear it popping from around the cat. I also noticed a fine dust like gold and silver glitter coming from the right muffler when I rev it up. Its not over heating or anything and i'm not getting any check engine light. When it runs good, it runs great! Any suggestions?? Thanks!

 

You probably have an ignition failure on the right bank. Either a coil "A" failure or a burned through Marelli distributor rotor, or both. That also usually means a melted down catalyst on that bank, especially with your "gold dust" comment.
I'd not run it any more until it is repaired, that will limit the damage.

 

Agree with XJRGUY. Definitely a famous Marelli failure. Please do not drive the car until you get it fixed. I had the same issue on my 92 and I foolishly drove it 1 mile home, after which the cat was so hot from the exploding unburnt fuel that it set the steering rack boot and chassis leg on fire. You have been warned.

 

Thanks for the quick reply! Ok, i'm taking your suggestions and not driving or starting it again. I did a bit of research and found a service bulletin that sounds like what i'm experiencing.

Electrical & Lights: ELECTRICAL SYSTEM:IGNITION

Service Bulletin Number: 1841
NHTSA Number: 10011894
Model Years Affected: 1994
Date of Bulletin: 02/2005
Bulletin Summary: INTERMITTENT POWER LOSS TACH DROPS TO ZERO REPOSITION IGNITION AMPLIFIER.

Is that coil difficult to replace? probably makes sense to replace both sides at the same time I assume?
Anyone know much about these bulletins? I assume its not like a recall and i'm not entitled to have this service done by the dealer.

Thanks all!

 

The bulletin refers to relocating the right control module (above the radiator) so that it doesn't come in contact with the underhood insulation blanket and cars from VIN 188105 to 194706. Couldn't hurt to look at yours.

I don't see where this was a recall. I think it's just a tech advisory. So, no, no free repair at the dealer.

You should pull the distributor cap and take a look at the ignition rotor and inside of the cap. 'Tis the rotors that generally fail and cause the dreaded Marelli Melt Down. That doesn't mean a coil or module *couldn't* be at fault, of course.

Cheers
DD

 

That repair [moving the ignition module] was a big deal back in the day. I think it would be a rare XJS that hasn't had that addressed before now. Given the age of the car, I think everything mentioned here should be addressed, rather than looking for the cheapest fix. Marelli meltdowns can be catastrophic! I have seen more than one get so hot under the car that the passenger compartment carpet and insulation caught fire. Please take heed!

 

Well, I pulled the dist cap and it looks ok from what I can tell. Unfortunately, when I pulled the "b" side coil wire, the entire tower on top of the dist broke off inside the wire. It looks like there may have been one or two sparks that contacted through the cap to that "b" side contact melting (really, just a tiny bit) the inside of the cap. The rotor looks good and the contacts have a small bit of build up but since its probably all original parts since it only has 40K on it, it doesn't look bad. Planning on replacing the cap, rotor, plugs and both coils (since i'm in there) later this week. Hopefully I caught it before it caused too much damage to the cat.
Keeping my fingers crossed!
Thanks all.

 

Well said! That should fix 'er up. Another word of caution, at least with the cap and rotor, stick with Marelli trademarked parts. Aftermarket or no-name parts, at least in this case, have a TERRIBLE track record. I'd also not get sucked in to the Bosch Platinum or "Split-Fire" spark plugs, stick with NGK. I think if you wander the forums, I'll be backed up on those counts, for the most part.
I'd also take down the bank one intermediate pipe and muffler, so you can look in at the catalyst from below. From your original post I'm expecting you to find it damaged. You never know, though.

 

I agree on doing it all at once. That's what I would do, especially if the age of all taht stuff was unknown

FYI, bona-fide Marelli distributor caps are no longer in production. The cap sold by Jaguar (for about $180) is the very same cap being sold under the Beck Arnely label for $50-$90. At least one vendor out there is selling the currently available Jaguar cap with an illustration of the true Marelli cap...so be careful of anyone advertising a genunine Marelli item. There's no point in paying more than you have to.

These replacement caps do not appear to be as high grade as the original but I guess all you can do is check its condition once a year or so and make sure all is OK.

The genuine Marelli rotor is still available, though, and if you order the Jaguar part, you get the real Marelli item

Cheers
DD

 

Welsh guy said the parts will be here Thursday. Thanks for all the help and advice! I'll let you know if that fixes the issue!

xjrguy, you suggested taking a look at the cat. how can I tell if its damaged? I didn't order that part in hopes it is still good enough.
plus $450 in parts pretty much tapped me out!!

 

It should look like a light gray fine mesh screen. If it is broken up or melted, it has to be changed. You can also take out the oxygen sensor and look thru the hole. There should be two substrates, one above the sensor and one below, and nothing but space in between.

 

Where is the service bulletin info located... web site ? Seems like a great place for info and Tech Help. Cheers

 

The full migration to the new technical information site is not complete as yet. I'm not clear how they will allow access to things like recall and service action bulletins. I believe anybody will be able to access them at some point.
Attached is the module relocation bulletin mentioned here.

 

ilfordboy - I found it on the safercar.gov website that someone sent me to. Unfortunatly, it doesn't have the full text version, but you can ask them for further research.

xjrguy - is that the full text pdf? I'm unable to open it cause the forum says I don't hav the rights. Am I doing something wrong? or is it cause i'm new?

 

That is the original full text bulletin. I guess you may have wait a couple of days before your full access kicks in, then it should be available to you.

Cheers,

 

Here is a link to the bulletin. Use it since you can't do it over the forum yet.

http://www.adrive.com/public/63f555f...272386136.html

 

Well guys, its been two months since the full ignition repair/replace. Of course I've only driven the car about 50 miles since then, but it seems to be holding strong! Thanks so much to all of you for the great help!

 

@hey_nav

Glad you are firing on all 12 cylinders again, it's a great feeling !