Q: Stuttering when idle but the revs sit steady at 900 rpm and there are no issues accelerating.

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My 2012 E220 diesel auto (40,000 miles) stutters when idle. The revs sit steady at 900 and there are no issues accelerating. The engine ticks over normall but the shake/judder is sporadic and random and feels like someone has pushed the side of the car when it does it. Any ideas?

My car has 40000 miles.
My car has an automatic transmission.

Hi there. Sounds like the lift fuel pump is malfunctioning or there is air in the fuel system. First, check the fuel level in the fuel tank and make sure that there is at least a half tank. Then check the fuel pressure on the engine and make sure that there is enough fuel pressure to the injection pump. Check the fuel filter and see when the last time it was replaced. If the filter is old, it will be dirty and can cause the engine to have a hesitation on an idle condition when the engine is demanding the littlest fuel consumption. If the fuel filter is replaced and there is fuel pressure to the fuel injection pump, then I recommend bleeding the fuel system at the injection pump and see if there is any air in the fuel system. If you need further assistance with your diesel engine surging at idle, then seek out a professional, such as one from Your Mechanic, to help you.

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