idle chit-chat

What should the idle speed be on a 2001 M600 ?

Mine has always been about 1,500 rpm, until after my last service when it went up to 1,750 (ish). This was fine, but it then started to creep up sometimes to 3,000 which was not good and even worse in the wet when it went even higher.

Anyway checked out my trusty Haynes manual, found the adjustment screw and turned it right down so that it idles nicely at around 750-1000. Seems to have cured the climbing, except in the wet when it still climbs up, but only to 1,500 which is OK.

Any ideas why the idle speed should climb when the engine is hot or wet ?

Is it normal ?


Cerebus the idle