VW Jetta Hybrid Fuel Mix Issues Fixed: Expert Tips

I had a similar issue with my 2018 VW Passat Hybrid with comparable symptoms. From my experience with hybrids, this definitely sounds like a fuel injection system problem. The check engine light was my first warning sign too, and I noticed the same jerking during acceleration. After scanning, my mechanic found a faulty fuel injector was disrupting the air-fuel mixture. The mass airflow sensor readings were all over the place because of this issue. The repair involved: Complete diagnostic scan, Cleaning the fuel injection system, Replacing one defective injector, Testing all spark plugs and oxygen sensors, Final computer reset and testing Total cost came to 515€ and took about 6 hours to complete. The car has been running smoothly since then with no check engine light issues. Before suggesting specific fixes, could you share: Have you had the diagnostic codes read? When was your last fuel system service? Does the problem get worse when the engine is cold or warm? What kind of fuel are you using? This would help narrow down if your issue matches what I experienced and provide more targeted advice.

Thanks for sharing those insights. My last service was actually 2 months ago, so I was surprised when these symptoms started appearing. I got the codes read yesterday, P0171 and P0174, pointing to a rich mixture condition. The problem definitely gets worse when the engine is warm, and I use premium fuel as recommended. Most concerning is that my mass airflow sensor readings are fluctuating wildly according to the scan tool. I checked the intake manifold for any obvious leaks and inspected all accessible spark plugs, but everything looks clean. Could a failing oxygen sensor be causing these symptoms even though the engine was serviced so recently?

Thanks for those additional details. The combination of P0171 and P0174 codes with fluctuating mass airflow sensor readings matches exactly what I experienced with my VW before the repair. While my initial assumption was the fuel injector, your symptoms actually align more closely with a failing oxygen sensor, despite the recent service. The fact that your problems worsen with a warm engine is a telltale sign. The mass airflow sensor readings are likely responding to incorrect data from the oxygen sensor, causing the fuel injection system to compensate incorrectly. After dealing with this on my VW, I learned that oxygen sensors can fail suddenly even after service. Mine failed just 6 weeks after a complete tune-up. The air-fuel ratio kept getting thrown off, triggering those same fault codes you mentioned. The repair in my case required: Replacing both oxygen sensors, Recalibrating the mass airflow sensor, Updating the engine management software Total repair cost was 380€, significantly less than my previous fuel injector issue. The check engine light cleared immediately, and the engine smoothness returned to normal. Those fluctuating MAF readings might also indicate a vacuum leak developing somewhere in the intake system. Worth having this checked while the oxygen sensors are being replaced.

Based on that feedback, I will definitely get the oxygen sensors checked first. The similarity between our symptoms, especially the fluctuating mass airflow sensor readings and rich mixture codes, makes a lot of sense now. I just scheduled an appointment for tomorrow to have both oxygen sensors inspected and potentially replaced. Will also have them check the intake manifold for vacuum leaks while they are at it. The total quoted cost is actually close to 400€, which matches what you paid. The fact that your VW had a sensor fail shortly after service makes me feel better about this happening so soon after my maintenance. Will update once I get the results, but feeling more confident now about the likely cause. Really hoping this fixes the rough running and power issues I have been experiencing with the fuel injection system.