MGSED

Hi, I've recently purchased an 07 GL420cdi. To be fair everything seems to function as expected, ride is unreal, but there's just a couple of small things, which compared with my C220 have me a little concerned. First, is the idle speed. sometimes when warm the idle is, as I'd expect circa 800rpm. but then others its 1100, both in park or neutral, and the only way to get it to return to 800 is to stop it and start it again. the other is on the down shift, normal braking, and it seems like sometimes there a slight (for want of a better description) "Klunck" which is felt under the car, I'd say Prop-shaft kind of feel (from driving 4x4's of old) Any ideas or advice would be appreciated.

alx

MGSED

In fairness the car has stood for a while, and the drives I've been doing are for over 30 mins but stop start. So I'm guessing a hard blast out would help? Tacho isn't out as the tone and feel to the engine is concurrent with circa 1k plus rpm. Was thinking idle control but when you turn off the engine and restart it the idle returns to normal.

lkchris

In cold weather, the diesel will by design start at a higher than normal idle. This always subsides very quickly, however.

MGSED

So today I've been driving tp wprk in the car circa 40 mins at various speeds but on every occasion possible I've tried to accelerate hard and then hold it in the gear to see if it will blow out any soot or deposits. So twice now the car has idled just over 600 rpm. After getting home, so 45mins drive approximately, i engaged park and it was idling at 800, i blipped the throttle and it went down to 600? Could this be a sticky idle control valve?