morning guys, I have a 2000 ML320 that surges at idle in park (1000-1200 RPM) and when I'm at a stop (600-700RPM). Thought it was bad gas, but it didn't go away on fill up like I was expecting it to. I am not sure what is causing it, it drives and shifts fine. Any help would be greatly appreciated. Thanks in advance.

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1993 300D 2.5 Turbo
Daily Driver.... 238,000 miles and counting (Gone for an '03 Camry)
2000 ML-320
New Daily Driver...139,xxx and still in one piece...