1993 Mercedes Benz 400sel

I have forwarded your question to our M/B tech. He will be with you shortly, thank you for your patience

A faulty fuel pressure regulator is common on this vehicle and will cause what you are describing (except for the ASR light). These regulators are known to leak internally and will cause rough and low idle, and no power. Also if you are smelling something similar to a rotten egg rather than gasoline you may have a failed catalytic converter that can also cause the same complaints. As for the ASR light you have a stored and current fault code that can be read from the vehicle with a MB handheld code reader (dealership item) however the Acceleration Slip Regulation (ASR) is probably not causing your issue as this is a component that is more related to the Traction system rather than engine performance. The reason they are occuring at the same time is related to the self check that the vehicle does when turned on rather than them being a cause and effect issue.

Can you indicate where exactly the gas smell is strongest on the vehicle. Is it closer to the engine by or gas tank. Are you noticing any fuel hitting the ground, like a fuel line leak. The intake backfire is a possible sign that the vehicle is running lean (possibley because of a fuel leak). Check along the firewall for leaks as often times they can go unnoticed along this area. Let me know what you find