Over-revving on start up M112

[KillerHERTZ]

Ive been meaning to make a thread on this since I got the car. - the same applied to my brothers W208 320

When I start up my car from cold I normally have to wait a good 1 or 2 mins for the Revs to reduce from 1500rpm to under 1000rpm. and if I move off before this braking is alot harder and more pressure must be applied.

Yet on freezing cold days I only have to wait around 10secs - why is this? surely it would take longer when its colder.

Is this system just to reduce wear and tear on the engine to get it up to temp? and will I do any harm by not waiting? my neighbours arent too please with me sitting their for a couple of mins with my AMG rear box making noises in the middle of the night

 

[seymansey]

The fast idle is normal, most of my previous cars had a 1500rpm fast idle for a few minutes. As for the mornings where i get in my C240 and drive off, there isn't anything abnormal about the braking when it has this fast idle. I'll check later when I go out, it should do it again.