I have a 1987 560 SEL. Does anyone know what a fuel mixture control unit is and where it's at? I guess its also sometimes called a lamba control unit(?)

I think i just replaced one on mine. the mixture control is the hole that you can access thru the air cleaner right in the middle. by using an allan (?) wrench you can adjust the fuel into the injectors. i think it is located at the fuel distrubitor on the passanger side, there is a black plastic gizmo about an inch high and 3 inches wide that is attached by 2 or maybe 4 screws located behind a plastic cover that is a little hard to see but with a knife you pry them (it?) off and remove the screws. I just put a used one on that came with a used fuel distrubitor. ( I PUT THE Fuel Distrubitor ON ONE CAR AND THE MIXTURE CONTROL (?) ON ANOTHER THAT WAS LEAKING GAS FROM IT) WARNING ...I AM NO MECHANIC AND MAYBE I DIDN'T EVEN REPLACE THE FUEL MIXTURE CONTROL? BUT I DID REPLACE SOMETHING ?? GOOD LUCK

yabass is correct about the mixture control unit. it controls the fuel addition as air enters the engine through it.

the lambda control unit is a black box full of transistors that is the electrical control portion for the fuel injection. the germans are so literal when the translate to english. good luck, chuck.

Do not play with that setting if you don't know what you're doing! Many people brought their cars to a point where they won't start after fiddling with the Lambda setting screw.
You will need to use a meter or a scope and understand duty cycle before you attempt this. Search this forum for good posts on this, there are plenty.