1995 Mercedes-Benz S500 Rotten Egg Smell

MERCEDES BENZ
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ORANUSS
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  • 1 POST
Hi,

I've been having a problem with my Mercedes Benz, S500 (1995) for the past several months...and despite having spent over 3K already no one seems to know what's wrong with it.

The car sometimes (although more often now than before taking it in for repairs) shakes, is slow to go (no power), and omits a rotten egg odor. No Engine light comes on.

The last Mechanic I took it to says it needs an overall tune up and wants to charge us 1K to tune the car up...I asked him to tell me whats wrong with the car and how much it will be prior to me spending 1K to just tune up the car and then finding out I need to cough up more for repairs...he insists it just needs a tune up.

PLEASE help on any advice you may have as to what this could be.

Also please note that multiple diagnostic tests have come back negative on what it could be (or so that's what they say)

You can email me your answers to: oranuss@yahoo.com

Regards,

O
Mar 16, 2006 at 4:09 AM
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GFIMOTORCARS
  • ✓Experienced Mechanic
  • 673 POSTS
The "rotten egg" sulfur smell is usually generated by high temperatures in the catalytic converter caused by excess unburned fuel going through the exhaust. The converter oxidizes this fuel, which generates the heat, and the high heat generates the smell. A little of this smell at start up is okay but if you are getting a very strong odor you may need a new catalytic converter to get rid the smell all together. As for the shaking and slow throttle response I would say this is all related. Your vehicle may be running very rich and if so is dumping unburned fuel into the cat which is causing the excessive smell. It would also be causing your poor response and shaking.
Jan 4, 2009 at 4:18 PM
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Suggested Repair

Diagnose a rich-running condition that is sending excess unburned fuel into the exhaust. That can overheat the catalytic converter and cause the rotten-egg smell, shaking, and weak throttle response. If the odor is very strong, the catalytic converter may need replacement.

Conversation Summary

The owner of a 1995 Mercedes-Benz S500 reports shaking, lack of power, and a rotten-egg odor with no check-engine light. Prior repairs and diagnostic tests did not identify the fault, and a mechanic recommended an expensive tune-up without explaining the cause. The expert says the sulfur smell usually comes from a catalytic converter overheating as it burns excess fuel, and that a rich mixture can also cause the shaking and slow response. A very strong odor may require a new converter.

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