1988 300SEL Low idle at operating temp
 

I know this is probably a can of worms and the idle is electronically controlled but you guys are pretty damn smart so maybe you have an easy solution.

Car starts and runs great but will fairly consistently drop to a low lumpy idle after it reaches operating temp. Only does it under load though, if its in neutral it will hold around 650-700. I replaced the plugs and wires yesterday and while I did clean up the contacts on the dist. cap, that component is well used. Would that be enough to offset the idle?

Starting to like this car.

The idle speed is controlled by the computer/idle control system....the idle quality depends on the condition of the electricals....plugs....injectors.....fuel quality.....etc...

Yeah I agree, I think I will go ahead and get the dist cap and rotor done and monitor the fuel quality before I worry any more about it.

I've replaced pretty much everything on our 300E (aside from the wires)....and it idles around 600 in drive....so smoothly that I can't even feel it. The most noticeable change in idle quality and performance was from using Redline SI-1 total fuel system cleaner.