Mercedes GLK Diesel Engine Running Lean Diagnosis

My 2011 Mercedes GLK with a diesel engine is giving me some trouble. It has about 210547 km on it. The engine seems to be running lean – not getting enough fuel. I've noticed reduced engine power, and the check engine light is on. The engine runs rough, and it sometimes jerks when I accelerate. I have already replaced the spark plugs. I am not sure how to diagnose this any further. Could it be the throttle body or the mass air flow sensor? Maybe even the catalytic converter? Any ideas?

4 comment(s)

I encountered a somewhat similar situation with my previous vehicle, a 2014 Audi A4. The check engine light illuminated, and the engine exhibited a lack of power. While the specific circumstances may differ, have you considered the possibility of a faulty fuel injector? I am uncertain if this aligns with your situation, but it might be prudent to explore this avenue.

Thanks for the suggestion. A faulty fuel injector is indeed a possibility I hadn't considered. Was the issue with your Audi A4 also intermittent, or was it a consistent problem? And did you notice any specific conditions that seemed to make the problem worse?

The issue with the Audi was indeed consistent, and grew more severe over time. Initially, the power loss was barely perceptible, but gradually worsened until the check engine light came on. I am not a mechanic, but my recommendation would be to take your Mercedes to a trusted workshop for a thorough diagnosis.

Thank you so much for your advice. I took it to my mechanic, and it turned out to be a defective fuel injector. The repair cost was around 515€. It is now running smoothly again.

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