Our Supercharged XJ8L suffered massive backfires/ missing/ restricted mode at 50 miles fuel left just after rounding a bend at 60 mph in cruise. Stopped, cut engine for 2 mins, then drove home perfectly normally. Disconnected battery overnight and put in more fuel. Car fine next day but got CEL after 45 mins driving. Fault was read as both Cats failure. Faults cleared several more times over 3 months but CEL always returns with Cats fault. 2 days ago, same catastrophic misfire/ restricted performance etc at 50 miles (again) after rounding bend. Car now in specialist Jaguar dealer. Left hand Cat broken with bits fouling sensor. Been cleaned and refitted. Dealer wants to replace Cat before going further. Misfire was indicated on 3 coils - now running perfectly after all faults cleared.
What caused the misfire and Cat damage??? I think its a fuelling issue. Does the Super V8 have a transfer pump (jet pump) between tank sides? Could it simply be a fuelling issue? Fuel filter has not been changed. Car is in excellent condition ex-Japan. Car is in New Zealand. Any help greatly appreciated. Are aftermarket Cats available - perhaps in USA?

 

Welcome to the forum PUSSS.

Aftermarket cats are available as a bolt-in product, but not cheap as they are a "performance" item.

I would just get an exhaust shop to weld in some generic 200 cell cats, you can pick them up for less than $150 per side, plus labour to weld them in

Magnaflow High Flow CAT 2 1 4" 200 Cell Metallic P N 59955M | eBay

The Supercharged cars have two fuel pumps, one on either side of the saddle tank.

But I don't see how insufficient fueling can cause misfires....

I do recall a collapsed cat causing bad misfires in one X350, it could be that the cat failed, which caused the misfires, not the cats being damaged by the misfires...

When you get a moment stop by our new members area ==>> New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum

 

I wouldn't hurt to change the fuel filter and use a bit of sea foam in your fuel every now and again.

 

There is a transfer pump in the tank. The tank "straddles" the driveshaft hump, so the transfer pump is needed to get the fuel on the wrong side over to the engine fuel pump on the other side in low fuel situations. Other than that fact, I don't know the details about it.

A misfire results in raw fuel dumping into the exhaust, and then the cat ignites it. The result is that a misfire situation can melt the vanes inside the cat in a few seconds. Your situation is a bit strange, as the misfire was "seemingly" due to a lack of fuel...odd that raw fuel would damage the cats in that case. There may be more to what is going on than simple fuel starvation...

 

Without replacing the cat(s) and then looking at the OBD data to see if it's running OK, plus waiting to see if any codes flag, you'll probably never know if the cat(s) was/were to blame. If new one(s) fix the fault then you'll know, otherwise hope for new code(s).

 

In my normally aspirated 04 VDP I had a P0420 code (right bank cat) that was caused by 7 of my 8 cylinders misfiring. Replacing the fuel injectors (or they could have been cleaned) with remanufactured ones fixed the problem and removed the code fault without needing to replace the cat. Fuel performance is definitely related to cat performance.

Just in case I needed a new cat, I found a direct-fit aftermarket cat made by Eastern Catalytic. However, I don't see a cat for your model in their catalog.

 

Many thanks people for your help. Will get onto sourcing a new Cat

 

New cats might solve the problem temporarily, but if you don't fix what caused them to go bad you'll probably lose them again. I think it would be worth paying the dealer to read the codes and offer a diagnosis. Just my opinion....

 

Give George at venom cats http://http://www.venomexhaustworks..../products.html a call

He made the 2 1/4 inch units for my XJ8 he also welded in the 02 sensor bungs one on each end

I then took the cats to my mates exhaust shop and he made me a duel out of the headers 2 1/4 inch down to an X pipe and new middle muffler

He can make 2 inch units as well cost me $370 including the bungs welded in and shipping to Queensland

Japanese imports have a notorious problem with cats must be something due to short trips cats not getting heated up properly can also be the cats got hit as well remember they are ceramic imagine dropping a ceramic coffee cup they eventually break and so do cats

I had a few Japanese imports in the 90,s had to replace the cats on them in those days we used to just unbolt them and run a broom handle through them
Now its a 10,000 grand fine no one will do it and I don't blame them