S320 cat question - PeachParts Mercedes-Benz Forum

amosfella · #1 02-28-2010, 05:52 AM

My 95 S320 has been slowly loosing power, but hasn't been throwing codes or having the CEL come on. I"m wondering if my cats aren't plugging up. I was thinking about removing the exhaust to see if they are plugged. If they are plugged, I was thinking about simply cutting open the cats and removing the honeycomb. There's no emissions tests in my province, and I feel no love for the EPA types, etc.
My question is, if I remove the honeycomb, is there a consequence for any sensors in the exhaust stream?? Will I be getting codes thrown up on a constant basis?? If there is a sensor in the system that would be effected, is there a way to override it??
Does anyone have experience with a car of a similar age??
I have not looked under the car to see if there is a post cat sensor either... I might do that in the morning...
Thanks in advance...

oldsinner111 · #2 02-28-2010, 05:15 PM

I cut my Toyota's off and sold it for $80. They are power robbing device's same for egr's. Would you want to breathe carbon monoxide,your engine does not want to.

amosfella · #3 02-28-2010, 05:40 PM

I know they're a power robing device, especially when they clog. But, I need to know if removing the honeycomb from the cat and welding it back shut will result in my have a continually lit CEL light...
If the CEL light is a reality, is there anything to do to override it... Checking the manual, it's inconclusive if there is a post cat oxy sensor, and I don't think I want to lay around in 4 inches of mud to find out...
Also, my fuel economy has been slowly declining as the power loss is happening. However, there is no discernible blow by when running the engine with the oil filler cap off, and no oil or coolant leaks I can find to indicate head gasket failure....

oldsinner111 · #4 03-01-2010, 04:53 PM

I know Mercedes does some test with a cat by pass pipe,on some engines.If it throws codes I don't know.However all my cars first thing I did was ditch the cat.Never had codes,in fact it stopped some.Power loss you may clean your air sensor in intake,behind air box.I have too cleaned oxygen sensors with throotle body spray,and let dry.

amosfella · #5 03-01-2010, 06:13 PM

Well, when I'm able to crawl under there in the next little while, if there is not a post cat sensor to bug me, they're being ditched...
However, I cannot afford downtime to figure out how to bypass a sensor, or such....
Has anyone ever tried using those o2 sensor extensions that take the o2 sensor out of the main exhaust flow to work around this problem??

Lowflyingbird · #6 05-14-2011, 07:10 PM

I too have a 95 S320 and noticing the same issues. I will be removing the mid muffler. Occasionally I smell a small amount of rotten eggs indicating the cats may be on their way out. and, Yes I have tried cleaner and Xylene.
Have you done anything since your last post, or has anyone else done anything?
Please post.

oldsinner111 · #7 05-14-2011, 07:15 PM

No cats,no center muffler.no codes pure power.

Lowflyingbird · #8 05-15-2011, 08:59 AM

Now I bust out the sawzall and the Mig welder!

oldsinner111 · #9 05-15-2011, 09:52 AM

If you should get a code from 2nd oxygen sensor,unplug it and unscrew it.Take fire prooft paint or exhause putty and plug up hole in sensor.All it does is turn on check engine light.I removed my check engine light bulb.Don't need the agrevation.

duxthe1 · #10 05-15-2011, 04:44 PM

Despite the bad rep of old catalysts, modern catalysts do not rob significant amounts of power. I've seen dyno sheets of catalyst deletes netting less than 5hp. They do a great job of preventing your car from being a gross polluter and removing it is just plain irresponsible. If there is a problem with your catalyst it will be because of a problem with the engine that has damaged it, otherwise they tend to have a long and efficient life. How about getting a professional diagnosis of your power loss instead of immediately deciding it would be a great idea to turn a clean car into a gross polluter?

Lowflyingbird · #11 05-15-2011, 06:55 PM

These is not one professional who is going to look at it and tell me they are fine, they will however see the possibility for profit. The common rotten egg smell accompanied by mild restriction is all any experienced mechanic needs.

I have also had vehicles run just as clean without them. If needed I will pick up a set of Magnaflow race cats which I bought in the past for another vehicle I had, ceramic monolith type. I have access to a friends shop who has an anaylizer, after that I will see if the car needs them. I weld all my own exhaust from stainless with mandrel bends. Obviously if the car throws a code I will install the aftermarkets.

These S class years seem to have an issue with the cats going bad. I have heard of more than a couple instances. Also a bad cat is not always caused by a bad running motor, many companies who make replacements only state there is a 50kmi lifetime for peak use, on orig or replacements.

To anyone reading, never gut a cat out. The void space becomes an echo chamber, and messes up the flow. If you want stealth then cut open the case place a pipe within, weld the case over it.