1990 300CE...Strong odor on exhaust...HELP!!!

[Benz300ce]

I just got my car 3 weeks ago and I noticed that there is a strong odor coming out of the muffler. When the car is parked and I step on the accelerator, I can see black stuff coming out of the muffler. I'm not sure if it's oil or carb deposit. I don't see any indicator light on my dashboard. I really don't know what's going on with this. If anyone can help me solve this problem, I would really appreciate it. Also if you have an idea on how much it would cost to have this fixed.

[sixto]

Does it smell like sulfur or rotten eggs? If so the catalytic converter is toast. Catalytic converters don't normally quit on their own. It's likely the engine is running rich (too much fuel) and even more likely the engine has an oil consumption problem from worn valve stem seals and/or valve guides. It makes no sense to replace the catalytic converter before you address the root cause.

How much? A catalytic converter is probably (wild guess) $800 installed at the dealer and half that at a muffler shop. Another $200 for an oxygen sensor that can't be too happy at this point. Valve seals can be replaced by an independent shop for around $400. Assuming your car has a 12 valve engine. Replacing the valve seals in a 24 valve engine will cost more.

Sixto
95 S420
87 300SDL

[deanyel]

My first step would be to see if you're getting any fault codes - either by taking it to a good independent shop or building the code reader (see archives). There's lots of fault codes that don't show up as a check engine light.