I recently experienced the “cherry red hot” catalytic converter problem as the A-bank ignition coil failed on my '90 V12 with Marelli. The converter innards are rattling so I assume the converter does not work anymore. What influence does that have on the engine, as the O2 sensors now provide different information to the ECU? Rough idle, lack of performance, rich running? I do not need to pass a smog test here so I would opt not to replace the converter if it has no negative influence on the engine.
Thanks for any advice
Stephan
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
It will obstruct exhaust flow. A good cat won’t because it has zillions of little passages through it, but a cooked cat will have melted the matrix and closed off a bunch of them. You need to take the cat off, gut it, and put it back on. The engine will run just fine.
Note that the chunks you’ll be busting out contain platinum. It’s pretty valuable stuff. I think there are outfits that will buy old cats to recycle the stuff.
Stephan28281,
My wife’s 1990 XJ-S convertible suffered an A bank Marelli meltdown at some point before we purchased the car in 2005. The car failed it’s first CA smog test at the Gross Polluter level. Suspecting a Marelli issue, I removed both sides of the exhaust system from the downpipes to the tail pipes to inspect them. The left side looked perfectly fine but on the right side both the front and rear catalytic converters were badly damaged and the front and rear mufflers had pellets and chunks of catalyst matrix in them. The downpipe had melted areas that closed off air flow bust you could see straight through the rear one. I shook out all that debris, replaced the two right side catalytic converters along with a bunch of ignition components (plugs, wires, coils, cap, rotor, etc), reinstalled the rest of the exhaust components and the car easily passed the CA smog test (and has done so every 2 years since then).
If I were you I remove the right side exhaust components, inspect them for the damage, remove any blockage or debris that might restrict airflow and then put everything back on. The O2 sensors and ECU won’t see anything wrong.