are aftermarket Cats okay on a 01 E320
 

recently I heard a rattling on my girlfriends car, so we took it into the exhaust shop and they said that the rear catalytic converters both are bad. we recently had the spark plugs replaced because we were getting a slight misfire at idle and the mechanic told us that the plugs were due to be changed anyways but the Miss fire was caused by a loose coil pack. The Shop told me that due to the misfire it could have prematurely damaged the cats.
replacement cats through mercedes with piping are 600 a side. Plus install
I'm a person who saves money for rainy days but at the same time does not spend money it does not have to be as I am on a budget like most nowadays.
my question to you is are Magnaflow high-performance catalytic converters okay to run in replacement of the Mercedes ones or am I going to have big problems with early failure and need to be replacing them soon again.

I don't see why it could not be made to work but you won't have the build quality of the original system.

yes you can,

the rear ones are easy anyway - just get two straight cats from a magnaflow, eastern catalytic or any other good brand catalog. They usually are less than 100/piece (lower with discount coupons if you can find one like advance auto parts etc)

get them welded in place.

The rear cats only are to clean whatever was left by the front cats. which isnt much anyway I even have seen some cars without those rear cats and they were perfectly fine. I have also witnessed a "noisy rear cat" that actually had debris of the front cat's broken honeycomb. But if you dont see any cat efficiency errors then Im assuming the front one is working - but usually a rogue misfire in this engine is due to a bad front cat.

The front cats are a bit challenging to replace with aftermarket as you need an offset type cat. The good bit is that the cats only see half the engine.


By experience - the absolute best cats are the rebuilts sold by MB. They are expensive though but fit like a glove and flow very nicely.

Davidlee, Any GOOD muffler shop should be able to help you. I don't know the "smog" requirements in OR but one has to keep them in mind and this is where the muffler shop comes in. I would think your biggest problem is finding ones that don't rust.
Anziani
'97 CL600 52K

oe is the best way to go. but what ever you decide replace the rest of the coils and wire set that will make ignition good and should make cats last longer also replace plugs every 80k not 100k

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.

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.