Ac/Climate control causing rough idle? - Mercedes-Benz Forum

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post #1 of 1 (permalink) Old 07-19-2010, 05:43 PM Thread Starter
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Date registered: Nov 2009
Vehicle: 2001 S55 AMG
Location: Westchester New York
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Ac/Climate control causing rough idle?

So I was looking into a rough idle I've been having this summer. I am up to 140k miles, and I changed my spark plugs about 20k miles ago but never my wires, so I thought maybe the wires were causing the rough idle.

By accident, this is what I discovered today: First, the rough engine only happens at idle, can be either in park or in drive with the car fully stopped. It's most "intense" after coming from driving and stopping, like at a light.

So, I had my AC/climate control on. (It was on low if that matters.) I turned it off to hear the engine better, and the rough idle immediately decreased! I believe it decreased to what should be normal for the car, or at least very close to the engine idling noise.

To double check, I turned the AC/climate control back on, and immediately the engine idles rougher, like something is working harder.

So...any idea as to what this could be? I assume it's not normal for the AC in hot weather to make more noise from the engine, correct? So could it mean some type of fan or AC component is starting to go bad? Any ideas? Can I completely take out the bad wires idea?

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