Arteon Power Loss: Fuel Mix Issue and Rough Running

I had a very similar issue with my 2017 Passat, the symptoms match exactly what you described. I have some experience working on cars but decided to let a professional handle this one due to the complexity of fuel delivery systems. The root cause turned out to be a faulty fuel injector that was dumping too much fuel, causing an overly rich mixture. The oxygen sensor readings confirmed this. My mechanic found the air-fuel ratio was way off spec, and the catalytic converter was getting damaged from the excess fuel. The fix involved: Diagnostic testing to confirm injector failure, Replacing the defective injector, Cleaning the remaining injectors, Resetting the engine management system Total cost was 515€ including parts and labor. The car runs perfectly now, no more stuttering or stalling. Before offering more specific advice, could you share: Current mileage on your Arteon? Are there any other warning lights besides check engine? Does the problem get worse when the engine is cold or warm? Have you noticed any unusual fuel consumption? The mass airflow sensor is worth checking, but based on my experience, the symptoms really point toward an injector issue, especially with that rich mixture code.

Thanks for the informative reply. My Arteon has 135119km and last service was done 2 months ago. The symptoms do match what you described. Though in my case, the problem is definitely worse when the engine is cold and gradually improves as it warms up. The check engine light is the only warning light currently on. I took it to a shop yesterday, and their initial diagnostic suggests its related to the intake manifold, with the oxygen sensor showing erratic readings. The air-fuel ratio is fluctuating wildly according to their scan tool. They mentioned something about carbon buildup possibly affecting the manifold runners. Did your mechanic check the intake system before replacing the injectors? Just wondering if I should get a second opinion before authorizing the repair.

Thanks for those additional details. The cold-running symptoms actually make an interesting difference compared to my case. While my Passat had similar issues, the problems were consistent regardless of engine temperature. The intake manifold carbon buildup you mentioned is actually a known issue in our engines, and it can definitely cause the oxygen sensor readings to go haywire. In my case, though the fuel injector was the main culprit, we did end up doing a thorough intake cleaning as preventive maintenance. Since your symptoms improve with engine warmup, this strongly suggests the intake manifold theory could be correct. Carbon deposits can restrict airflow when cold, causing the mass airflow sensor to send incorrect readings to the engine computer. This throws off the fuel injection calculations and creates that rough running condition. For 135000km, carbon buildup is very plausible. I would still request they verify the injectors while they are checking the intake, when my injector failed, it also caused the oxygen sensor to show erratic readings. Given that your check engine light is on and the diagnostic shows air-fuel ratio issues, having them do both: Intake manifold cleaning, Fuel injector testing This should cover the most likely causes. The total job might run around 400-600€ depending on what they find, but its cheaper than replacing parts unnecessarily. What were they quoting for the intake manifold service?

The symptoms match perfectly with what I experienced. My Arteon mileage is indeed 135119km with maintenance done 2 months back. The cold running issues definitely point toward the intake manifold theory, especially since it improves as the engine warms up. The shop quoted 580€ for a complete intake manifold service including cleaning and inspection of related components. They explained how carbon deposits in the manifold runners could be affecting air flow and causing the oxygen sensor to report inconsistent air-fuel ratio readings. Still, your experience with the injector problem makes me want to ensure they thoroughly check the fuel system too. I will request they test all injectors while doing the intake work, just to be thorough. Better to catch any potential issues now rather than having to go back for more repairs later. The combined intake and injector inspection should help identify the root cause. The shop said they can do both checks for about 650€ total. I will schedule it for next week and update once I know more about what they find. Thanks for sharing your similar experience. The detailed comparison really helped me understand what might be going on with my engine.