VW Eos Diesel Performance Issues, Power Loss & Rough Idle

I had a very similar issue with my 2011 VW Passat diesel last winter. The symptoms you describe match exactly what I experienced, poor performance, increased fuel consumption, and rough running, particularly with cold starts. After some diagnostic work, my mechanic found a faulty injection valve that was causing an inconsistent air-fuel ratio. The rich mixture was affecting engine performance and causing the check engine light. The repair involved replacing the defective injector, which came to 515€ including parts and labor. Before making major repairs, it would be helpful to know: Current mileage on your Eos, When was the last time you changed the air filter, Any other warning lights on the dashboard, Are you using quality diesel fuel, Have you noticed any unusual exhaust smoke The catalytic converter could also be affected if this issue has been ongoing. Regular maintenance of the intake manifold and fuel system components can help prevent these problems, but injector issues are sometimes unavoidable. This type of repair requires specific diagnostic equipment and expertise. While I have some experience with VW diesels, I recommend having a certified mechanic perform a proper diagnosis using their diagnostic tools to confirm the exact cause.

Thank you for sharing your experience. My Eos has 14761km and just had its annual service last month. The check engine light started appearing right after a cold morning start. The engine feels particularly rough between 1500-2500 RPM. The fuel injectors definitely need inspection, as the poor performance and rich mixture issues point to fuel delivery problems. Running some tests would help identify if its the intake manifold or individual injectors causing the trouble. The car still has its original catalytic converter, and the symptoms suggest it might be getting clogged due to the rich fuel mixture. The declining fuel economy and power loss are classic signs of this type of issue. Would you mind sharing what diagnostic codes your mechanic found during the repair? This could help narrow down whether I am dealing with a similar problem.

Thanks for the additional details about your Eos. My Passat showed diagnostic code P0172, which indicated a rich fuel mixture in bank 1, along with a P0300 for unusual misfires. These codes helped pinpoint the faulty injector. The RPM range where you notice the roughness is very telling, exactly where my car struggled too. The rich air-fuel ratio was most noticeable in that mid-range, causing the engine to run inconsistently. Your relatively low mileage suggests this might not be normal wear and tear. Since the issue appeared suddenly after a cold start, I suspect a failed injector rather than a clogged catalytic converter, though both can present similar symptoms. My fuel economy had dropped about 20% before the repair. One quick check you can do: let the engine idle for a few minutes and watch if there is black smoke from the exhaust. This was a clear sign of the rich mixture in my case before the repair. The check engine light appearing right after service is interesting, there could be a connection. Have you checked if any work was done on the fuel system during the service? Sometimes disturbing these components can trigger underlying issues.

I appreciate the detailed comparison to your Passat issues. The diagnostic codes you shared definitely align with what I am experiencing. The black exhaust smoke test is particularly helpful, I just checked and noticed darker smoke than usual during idle. My service records show they did not perform any fuel system work last month, just routine maintenance including an air filter change. However, the timing of the check engine light following the service does seem suspicious. Based on our similar symptoms, especially the rough running at 1500-2500 RPM and the poor fuel economy, I will have my mechanic focus on testing the injectors first. The air-fuel ratio being off in this specific RPM range really points to injection problems rather than something in the intake manifold. I will schedule an appointment to have those diagnostic codes read and the injectors tested. The repair cost you mentioned of 515€ helps me budget for what might be needed. Hopefully catching this early will prevent any damage to the catalytic converter from the rich mixture. Thanks again for the helpful insights. This gives me a much clearer direction for addressing the problem.