I have a 1990 560 SEL that I'm trying to get a few bugs out of. I fixed the heat thanks to a tip on the monovalve. I had an annoying high speed vibration which I cured by cleaning the backs of the wheels and rebalancing them. One problem I still haven't fix yet is the idle. I checked the control valve for power.The ohms and volts where both fine. I checked for a vaccum leak and didn't find any. I checked the overvoltage relay, that seemed fine. The only thing I didn't check was the control module, because I wasn't sure where it was located on a 1990. And I'm not sure what to fix when I find it. If anyone has any suggestions, I would appreciate them! Thanks!