230K M111.975 unstable idle and vibration , help
Thread Starter
Newbie
Joined: Oct 2025
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W208 230K Sport
230K M111.975 unstable idle and vibration , help
Hi guys the car has 57000km, it has been stopped for many years and has been doing a tune-up, I have replaced all the fluids, filters, fuel pump, spark plugs, fuel filter, mass air flow meter, MAF sensor, as soon as I installed the MAF sensor I disconnected the battery for 10 minutes when starting the car, those oscillations and vibrations were felt the same at idle, the only positive thing I felt is that when driving the car felt more alive and much more cheerful, the engine previously also felt somewhat lazy, I do not have much mechanical knowledge and that is why I come here to see if you can help me and guide me in the diagnosis, I feel very frustrated with this problem, I show you 2 videos that I made so you can see how strong the engine is at idle, when running it feels good although I admit that I feel a little disappointed in the sensation regarding its 193hp
Last edited by Clk230_bcn; Oct 11, 2025 at 03:07 PM.
Out Of Control!!
Joined: Apr 2019
Posts: 12,002
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
I don't know your engine specifics... however by listening to your two video investigation, we hear the idle ups and downs
have you physically checked the fuel pressure delivery ie. pump or regulator ?? Is that a returnless system??
Don't replace parts blindly... try to evidence the available fuel pressure. Good luck
have you physically checked the fuel pressure delivery ie. pump or regulator ?? Is that a returnless system??
Don't replace parts blindly... try to evidence the available fuel pressure. Good luck
Last edited by CaliBenzDriver; Oct 11, 2025 at 04:24 PM.
Super Member
Joined: Jun 2025
Posts: 784
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From: USA
It sounds like you have an air leak after the MAF sensor. Check all the intake hoses and connections you touched during the tune-up. A leak there causes a rough idle.
The engine feeling more lively when driving is a classic sign of this. The leak throws off the air/fuel ratio at idle.
The engine feeling more lively when driving is a classic sign of this. The leak throws off the air/fuel ratio at idle.
