1987 Mercedes Benz 560sl idle

The idle air control (IAC) motor is supposed to raise the rpms when cold then lower them. With the vehicle running at idle unplug the IAC and then plug it back in. See if it changes the idle. You also might want to take it off and look to see if theres a lot of dirt in the part that goes in the intake. And lastly check for a vacuum leak with everything back together and some carb cleaner. With the car at idle and warmed up, spray around the top of the motor and on vac lines. A raise in rpms will indicate a vac leak.

Thanks. What about the idle modulator behind the glove box. Any opines about that.

I own a 91 bmw myself and you know as well as I do that the old one scan be tempermental but if youre like me, you love the car. If you've got one or theyre readily available, replace it and see. Im not an advocate of just changing parts but on cars with this much age and from this far away, it's hard to pinpoint. I hope ive helped at least a little