I just got my 1999 S500 back out of the shop and I was sitting in the driveway with the car running at idle. I turned the stearing wheel back and forth and noticed that the RPMs dropped and surged back up and then back to normal idle when I stopped turning the wheel.

What would cause that?

 

I have never really paid attention before. Is that normal?

 

yes its normal. now the newer mercedes have electric steering.