Quote:
Originally Posted by 97 SL320
A cat will melt due to a miss fire but generally does not break apart, thermal cycles / thermal shock will break a cat.
At least on my 97 SL320 ( M104 inline 6 with ME 2.1 injection ) , if you lift an injector wire / short a plug wire to create a miss fire, that cylinders fuel will be cut off after a few seconds to prevent cats from melting. This strategy might be on your system as well.
Some cars get really fussy when a cat isn't exactly as OE and throw a catalyst efficiency code.
I'd split the exhaust and clean out any loose parts. Mom and Dads 99 Blazer has a breaking apart rear cat and the pieces now reside in the muffler. . .where they continue to do their cat job and are heating the muffler up enough to balloon it. It still passes cat efficiency OBD tests so I leave it go.
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the M112 engine also cuts out the cylinder if a misfire is detected, just to save the cat.
I have seen quite a few M112 engines with aftermarket welded cats with no problems at all. The front ones are harder to weld, the welder usually tacks it in place, then removes the pipes and completes the welds on a bench. after bolting back up the pipes are then welded to the lower side.