I just bought a 90 560 SEL When I start up cold just turn the key she fires off no problem but I notice a little ruff and the rpm are low about 500 and then she gradualy smooths out within a minute of run time and the rpm go to about 650 is this normal I would think that engine would start at higher Idle when cold and then drop down to normal after warming up, this is all without touching the excelerator pedel any suggestions
Bob

 

Ok I found what the problem is. When I change sparks plugs i noticed one of the plugs were a little wet with fuel so I proceeded installing new plugs but this did not solve the idle problem. I then proceed to change out the injector for the cyclender that had the wet plug this made and improvement not as ruff and then proceeded to adjust the fuel/air mixture setting and the engine smooth out,like a rock. Now when I start the engine the rpm's go to 1200 and then slowly back to 650 and the Idle is smooth.
Bob

 

good job.
the engine is not ruff anymore even without touching the excelerator pedel. the cyclender now runs good.