VW Eos Power Loss Points to Lean Fuel Mix Issue

I had similar symptoms with my 2011 VW Golf GT. After experiencing power loss and rough running, the check engine light also came on. As someone with some hands-on experience working on VW engines, these symptoms immediately pointed toward fuel delivery issues. The workshop diagnosed a faulty fuel injector that was not spraying fuel properly, causing an incorrect air-fuel ratio. The oxygen sensor readings confirmed the lean condition. The diagnostic revealed misfires due to the defective injector, which explained the jerking during acceleration. The complete repair, including parts and labor, cost 515€. They replaced the problematic fuel injector and performed a thorough fuel system cleaning to prevent future issues. Before offering more specific advice for your case, could you share: Current mileage on your Eos, Are you noticing any specific RPM range where the problems are worse, Does the engine misfire more when cold or at operating temperature, Have you had any recent fuel system maintenance This information would help determine if your symptoms match what I experienced with the faulty injector or if other components like the catalytic converter might be involved.

Thank you for sharing your repair experience. My Eos has 90949km and the last service was 6 months ago. The symptoms are definitely worse when the engine is cold and particularly noticeable between 2000-3000 RPM. The engine misfires and hesitates most during this range. No special fuel system maintenance was done during the last service. Your experience with the fuel injector issues sounds very similar to what I am experiencing. The workshop quote I received mentions checking both the mass air flow sensor and oxygen sensor first, as they suspect the lean condition might be caused by incorrect air-fuel mixture readings. They estimate costs between 400-600€ depending on which parts need replacement. Based on your case, I will have them inspect the fuel injectors as well. This might save some diagnostic time.

Thanks for the additional details about your Eos. The symptoms you describe, especially the cold-start issues and problems in the 2000-3000 RPM range, are textbook signs of fuel delivery problems. In my Golf, the faulty fuel injector showed similar behavior. The workshop approach checking the mass air flow sensor and oxygen sensor first makes sense since these components directly affect the air-fuel ratio. However, my experience suggests inspecting the fuel injectors should be a priority, as dirty or failing injectors often cause these exact symptoms. After my repair, I learned that maintaining clean fuel injectors is crucial. The technician mentioned that modern direct injection systems are particularly sensitive to carbon buildup in the intake manifold, which can affect how the fuel injectors perform. The quote range of 400-600€ aligns with what I paid. If they find similar issues to my case, replacing the problematic injector and cleaning the fuel system should resolve the rough running and power loss. The spark plugs should also be inspected since a lean condition can affect their performance. One suggestion: Request they perform a fuel pressure test. This helped identify my injector issue quickly and might save you diagnostic time and money.

Thanks for all the valuable input. The symptoms you had with your Golf match mine perfectly, so I feel more confident now about the potential fuel system related cause. Your point about the cold-start issues being typical for fuel delivery problems is particularly helpful. I will definitely mention the fuel injector problems you experienced when I take it to the workshop tomorrow. The suggested fuel pressure test makes a lot of sense to narrow down the issue quickly. The quoted price range seems reasonable based on your repair costs. I am glad I asked here first, knowing that both the oxygen sensor and fuel injectors could be causing these lean running conditions will help during the diagnostic discussion. My main concern was a failing catalytic converter, which would have been much more expensive to replace. But given how similar our symptoms are, especially the RPM-specific issues and cold-start problems, I am now fairly confident it is related to the fuel delivery system. I will schedule the repair and make sure they check the whole fuel system, including injectors and spark plugs, rather than just focusing on the sensors first.