our story so far....
 

Well, I have to admit... I gave up. I took it in to autobahn motors in louisville. which is actually a good thing, they found a leak in my rear diferrential and a bad flex disc and changed it. So far they have replaced the Idle Air Control valve and the fuel pressure regulator, they still haven't got the idle where it should be and are still troubleshooting. I will post the fixes as soon as I get it back. While the 5 mile walk to formation every morning really sucks, I'd rather do without the car and get it fixed. I can't say anything bad about Autobahn. they are very knowledgeable, helpful and even give military the MBOA discount... not that I need it I've been a member since before I owned a benz :D Hell, Don even gave me a ride to the airport to meet my wife when I dropped off the car.

the saga so far
 

Well, I got the SL back from autobahn. Wow. I thought the car was fast before... I had no idea how fast it is supposed to be. They replaced the ICV, fuel pressure regulator, the engine vacuum hoses and the seals below the intake manifold. It turns out the previous owner developed an idle problem and instead of tracking it down and repairing adjusted everything around the problem, so every time they would fix something the would find something else wrong..... 14 days of troubleshooting. The worst was the random adjustments to the TPS the PO had done. It was very difficult to get that reset to the factory specs. but... the idle is now smooth as silk, the stalling and surging are gone and the only vibration in the car are due to the motor mounts and subframe mounts. I also definately need new shocks. unfortunately I still seem to be unable to start the car when it rains, so I bought a new ignition coil, distributor cap and rotor. I just finished installing them so I now need to find someone to get a jump start from to see if the problem is solved. If it is, all I need are the mounts, shocks, a hard top and some minor cosmetic things and the car will be as perfect as I care to make it. Thanks to everyone on the forum who offered advice. I really appreciate the help

I'm having almost the same problem with my 560SEL 1989 and no one could fix it!