leaschmitz1

Mercedes R Klasse Engine Power Loss and Whistling Noise

My 2009 Mercedes R Klasse with a gasoline engine is acting up. The check engine light is on, and it feels like it's lost power. Engine response is terrible, sometimes it stalls when idling. Fuel consumption has gone way up. There's a whistling noise when I accelerate. I suspect the boost pressure system. Could it be a defect in the wastegate valve? I've been reading about issues with the throttle body, turbocharger, MAP sensor, and intercooler. Anyone have similar experiences?

4 comment(s)

Sounds familiar. I had similar symptoms on my old Saab. Reduced power, weird noises under acceleration. On the Saab it was a cracked intercooler hose. Check your hoses and connections related to the intercooler and turbocharger for leaks. A leak anywhere in the system can cause a loss of boost pressure. Have you checked your MAP sensor readings? A faulty MAP sensor could also cause some of those issues.

Thanks for the input! When you say 'MAP sensor readings,' what exactly am I looking for? What's a normal range, and how would I even test that? I'm not super familiar with that sensor. What does MAP stand for?

MAP stands for Manifold Absolute Pressure. Basically, it measures the pressure inside your intake manifold. As for normal range, it varies depending on your engine's load. You'd need an OBD2 scanner that can read live data to see the values. Compare those values to what the service manual says is expected at idle, during acceleration, etc. Since your symptoms are pretty severe, I'd recommend a proper diagnosis at a workshop. A boost leak test would quickly pinpoint the problem.

Okay, thanks for the help and explaining the MAP sensor stuff. I took it to a local shop, and you were right. They did a boost leak test. Turns out the wastegate valve was faulty. Repair cost me 860€, but at least it's fixed!

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