I would keep the Marelli, once sorted they are extremely reliable.

The modules are BOSCH 0227100142 and are readily available.

So BOTH modules are doing the same thing - I suspect NOT, I would be looking at what was common between them:
Wiring harness
VR sensor

 

I 100% agree, Warrjon.

Greg

 

Update: I just got the car back from the mechanic; sadly it was with a tow truck.

Months ago I was told that the car had an ignition problem and that he was going to change the modules or redo the whole system altogether. I told him to take his time because he has a very busy shop and I was in no hurry to get the bill

But after 6 weeks of radio silence I gave him a call.

After our last phone call he did some more tests on the engine. He told me that he only had 10 inches of vacuum at the engine where he should have had at least 20. He also pulled some more plugs and took compression tests and his conclusion was that the car either has a broken camshaft or that it jumped time. (mind you I didn't tell him that I had been told it had jumped time because I wanted him to look at the thing objectively)

He offered to replace the engine for $3000 plus the price of a used engine and with that the old girl got towed home.

So here I am back where I started months ago.. With a broken car that now two jag mechanics insist has jumped time. I'm thinking about selling it. I have one jag that sucks up all my money already and if i can't afford to fix this white one theres no point to keeping it

 

I was told the same thing. The shop that had the car, replaced amps, coils, ignition wiring harness, Marelli ecu, as well as other things that didn't need replacing. Their thoughts were it jumped time. I don't know the experience of others, but I've not seen over about 12 inches of vacuum on any of my v12s. The short answer? Turned out to be the rear sensor was too far away from the flywheel.

I just simply don't believe a Jaguar V12 jumps time. I know a guy who drove one with a broken tensioner so long, that the whip of the chain wore a hole in the timing cover.

I am a compression test guy. Its almost always my first test before I proceed. Would be glad to discuss. I try not spend a penny on anything until I know my money is doing something in the right direction

 

I agree, These engines are ALMOST bullet proof.

I would pull; all the plugs and check and/or replace them. Check both front and rear crank sensors, to start with.

 

Wow, this is really interesting. Of all the things our cars are notorious for, jumping time is definitely NOT one of them. Those chains seem to last forever...

 

Hey everyone I'm back to this thread with another chapter to this story which is still ongoing. The car's been sitting and my '88 xjs failed CA emissions testing so I figured I'd pull the cats off this '90 since it didn't look like she'd be needing them. Decided not to sell because I seriously don't believe these engines can jump time and I want to get to the bottom of this thing.

What I found is the answer to the question I had near the beginning of this thread. If you remember the passenger side exhaust had nothing coming out of it.

Well this reason for this is that the cats on that side of the engine have completely melted down! Chunks of the catalyst came falling out when I separated the secondary cat from the primary.

It has me back to believing I have a marelli failure on my hands and the strange behavior of the engine is because that side was blocked and the engine could not breathe.

I'll be back with more soon but on a side note I still need new secondary cats for my '88 P/N CBC 8212 anyone know where to find them new or used?

 

a plugged cat will screw things up for sure.
If you think that bank isnt firing put an induction timing light on that side. If it flashes then you should have spark. that might be previous damage.

 

so much for trouble free Marelli igniton, and useless cats.

if it were my car, i'd run as close to a full flow exhaust system with out outrageous sound, and i.m sure with a standalone ECU it would meet Texas emission tests!

a simple remap of the engine computor!

 

You have made progress after the quoted post.

But ... if the shop was the same shop that tried the first time and ended
up with the pink slip, there was really no point in expecting a different
diagnosis than they made to the original owner.

Sounds like they tried to sell the same job to the original owner, he bailed,
and bought the '96.

I think Grant suggested removing the cats in order to test very early in
the thread right after the video of the imbalanced exhaust and mention
of red hot cats.