Frequent check-engine light and limp-mode, especially on bump roads - solution.
 

I don't remember if I've posted this before, so excuse me if I have.

When I first got my SLK320, I kept getting a check engine light and the car would go into limp-mode, usually if I hit any kind of bump on the road.

The connection between the air box and the throttle body was dry-rotted, and bumps in the road would open a gap allowing un-metered air in.

To fix this, I cleaned one surface and made a thick seal with sensor-safe silicone, then greased the surface it mates to and gently put the air box back on. After a day or so to finish out-gassing, presto: New air boot and no more check-engine and limp mode.

The air box can be removed and put back on entirely without tools--possibly part of why the boot is a vulnerable to failure--but it does make this fix easy to implement.

Thanks for sharing!