Have just acquired an 2007 ML 320 cdi which is in very good condition with full MB service history , only 42 k miles and serviced only 500 mls ago. The idle speed ( about 900 ) has been checked after I noted before collection that I felt it was too high ( was OK according to the garage who sold it to me ) Have done about 300 miles in it and it still idles at about 800 to 900 revs generally but today was at 1100 when I stopped after driving 60 miles . On restart a couple of minutes later it was down to 850. Also when using a full throttle there seems to be a bit of a vibration through the throttle pedal. Engine seems to be pulling well and is definitely not misfiring and is very smooth otherwise. Getting about 31 mpg on motorway at 65/70 mph , 32 mpg cross country on A roads at 45 mph ave. As it is going back next week to have Glow plug / or g/p controller changed as light stays on for 1 minute after starting and a non working Parktronic fixed there is another problem I would like to get it sorted at the same time. Maybe I would be best to get it on Star at an Indi before going to the garage Any thoughts?