456 Cats catching fire

Ouch.

It is a known problem with these cars, unfortunately.

Search "slow down light" here for threads that talk about it.

Good luck.

 

Well the slowdown warnings are known, but in most cases they're false alarm because of moisture getting in the little ecus. Unfortunately in this case it wasn't false alarm.
It is possible something melted in the wiring loom, you need to check underneath, also what got lit up. And for possibly missing heat shielding. As for the symptoms, maybe the spoiler motor got overheated by the exhaust. I believe it resides on that side; so the issue may just be that motor and the hazard warning has another cause. Those motors are volvo 480 headlight motors. You do need to search as some parts suppliers see that it also fits a Ferrari as a reason to ask very high prices for them.
Then there is the reason for the overheating cat, this is most probably some kind of misfire in the engine that caused unburned fuel mixture to enter the exhaust. If that happens it gets burned in the cat, overheating it. The cat is probably a write-off at this point.

 

This is speculation only, but you could have lost ignition on several cylinders on the passenger side, and the ECU continued to inject fuel, which then ignited in the cat. Was it running rough prior to the Slowdown alarm coming on?

That, or the exhaust on that side became very restricted somehow which caused the cat to overheat.

The "Slowdown" overtemperature alarm/shutdown system caught it, but it was apparently too late to prevent the fire.

Unless you really know what you're doing, suggest you leave the battery isolated, and get the car flatbedded to a specialist. Don't try to start it, and if it were me, I'd get the car out of the garage and away from the house.

 

Well the slowdown warnings are known, but in most cases they're false alarm because of moisture getting in the little ecus. Unfortunately in this case it wasn't false alarm.
It is possible something melted in the wiring loom, though it can also be the the spoiler motor got overheated by the exhaust. I believe it resides on that side; so the issue may just be that motor and the hazard warning has another cause. Those motors are volvo 480 headlight motors. You do need to search as some parts suppliers see that it also fits a Ferrari as a reason to ask very high prices for them.
Then there is the reason for the overheating cat, this is most probably some kind of misfire in the engine that caused unburned fuel mixture to enter the exhaust. If that happens it gets burned in the cat, overheating it.

 

Somehow my post got doubled! Anyhow, you're in the UK and the passenger side is obviously the other side.
As for the cat, it may be possible to get a ceramic cat core or sport cat welded in place of your current unit. Pay attention to regulation, in some countries there need to be official markings on the cats, I don't know about the UK. A good exhaust specialist should be able to help you further. It's only 2.75 liters displacement / 220hp per bank.
And that could be a good moment to look into the cars' soundtrack and have straight pipes installed instead of the center resonator, too.

But let's focus on getting it to run properly again first. Did you feel any hesitation when it was giving the slowdown warnings?

 

The cat in itself cannot catch fire: if it did it must have had unburnt fuel, coming from some units not firing properly or from leaking injectors.
The cause of the fire is somewhere else and needs to be investigated.

 

My 456 cat. did not catch fire, but it did burn a hole through the metal housing of the catalytic converter. I replaced both cat's with Xost Sport Cat's. Xost appears to be the only aftermarket supplier for 456 cat's and are MUCH less expensive than Ferrari cat's. I also used this opportunity to replace the central muffler with straight pipes.

 

Yes. Actually had flames shooting out the passenger side. Had a thread on here thanking another FC member who followed the car home, MIDNIGHT, with wife at the wheel [I was at home] and gave her a drop off at home.

Had to replace the CAT which is very expensive in the CA's legislated market.

The M series CAT can be substituted, but one will need to weld up one of the sensor holes as the M had an extra.

NA market shows varried prices and entirely depends it seems on supply/demand of which side is needed.

I'd check the exhaust manifolds too, as those are probalby toast. 456 had no alternative replacement manifolds either from the 550 series or even the M series.

NOT A CHEAP FIX.

 

EXACTLY! These things catch on fire when unburnt fuel is dumped into a hot core. No other reason. You need to find the cause.

 

Let's not get overly concerned. It is a cat and probably some wiring damage. And possibly some added cost of straight pipes.
Apart from the cat, that should not cost an arm and a leg, and for the cat I see there are alternatives.
I would not worry about exhaust manifolds, I believe it's unlikely for those to be affected.

 

I had a similar problem 6 mos ago,but damage a lot worse as I was on the freeway when it started.According to the mechanic the wrong battery was in the car causing low voltage to the passenger side bank of cylinders.This shut down that bank ,but ecu kept pumping in fuel whuch ignited in cat area

 

Moral of the story: disregard a "SLOW DOWN" light at your peril.

 

I had one that continualy overheated the right side cat. After a week of testing everything, I pulled the intake and checked the coolant temp sensors..One was open curcuit, thus the ecu sees -40 degrees, and dumps huge amounts of fuel. Replaced the sensor, drove the car around for a week, no issues after that. Customer sold the car shortly afterwords. He was too scared to drive it.

 

Have a look anyway, PITA to get there but def worth a look. Sure, the CATs got fuel and toasted themselves and trailing parts, but check the manifolds.