VW Taos Lean Running Issue: Fuel System Troubles

Having dealt with very similar symptoms on my 2021 VW T-Cross with the 1.0 TSI engine, I can share my experience as someone with some hands-on car maintenance knowledge. The symptoms you describe match exactly what I encountered, rough running, jerking during acceleration, and the check engine light. Initially, I thought it might be related to the throttle body or air-fuel ratio issues, but after diagnostic testing, it turned out to be a faulty fuel injector. The workshop performed: Full diagnostic scan, Fuel pressure testing, Air-fuel ratio measurements via oxygen sensor data, Individual cylinder performance tests They found one injector was not atomizing fuel properly, leading to incomplete combustion. The repair included: Replacing the defective injector, Cleaning the fuel rail, Computer reset and adaptation Total cost: 515€ However, to provide more specific advice for your case, could you share: Engine size and type, Current mileage, Any recent maintenance work, Specific error codes if you have them, Whether the problem is constant or intermittent These details would help determine if your issue matches what I experienced or might be caused by something else in the fuel delivery system.

Thanks for sharing your experience. Just had my latest service 2 weeks ago at 129910km. After reading your post, I had a diagnostic scan done and got error code P0171. The mechanic connected it to the mass air flow sensor and a vacuum leak near the intake manifold. The rough running and lean condition improved after cleaning the MAF sensor, but the check engine light returned after a few days. Think I might need a deeper inspection around the intake system and oxygen sensor to fully resolve it. Will have the shop do a smoke test to check for vacuum leaks next week.

Thanks for the update on your VW Taos. On my T-Cross, cleaning the mass air flow sensor also provided temporary relief, but like yours, the issues returned. When the check engine light came back on my vehicle, the mechanic discovered that while the MAF sensor readings had improved, there were multiple small vacuum leaks around the intake manifold gasket. A smoke test revealed leaks at both the intake manifold gasket and a cracked vacuum line near the EGR valve. The combined issues were causing incorrect air-fuel mixture readings, making the ECU compensate by running lean. The full fix involved: Replacing the intake manifold gasket, Installing new vacuum lines, Rechecking the mass air flow sensor, Testing the fuel injectors again to be thorough Total repair cost: 390€ With error code P0171 specifically pointing to a lean condition, these vacuum leaks are often the culprit even after addressing MAF sensor issues. Since your vehicle is showing similar progression to what mine did, having that smoke test done is definitely the right next step. If they do find vacuum leaks, make sure they check all the surrounding components while the intake is apart, particularly the throttle body and any connected vacuum lines. This prevents having to take things apart twice if there are multiple wear points.

Thanks for the detailed input everyone. After getting the smoke test done, they found multiple small vacuum leaks, just as suggested. The catalytic converter was also showing signs of damage from running lean. The final repair included: New intake manifold gasket set, Replacement of 3 cracked vacuum lines, Thorough throttle body cleaning, New oxygen sensor (upstream), Catalytic converter inspection Total cost came to 820€ with parts and labor. The mass air flow sensor readings are now stable, and the engine runs smoothly with proper air-fuel ratio. No more check engine light or jerky acceleration. The comprehensive testing and repair approach definitely solved what turned out to be multiple connected issues. Will keep monitoring the engine performance, but so far everything points to a complete fix. Really appreciate the guidance that helped identify the vacuum leak connection to the lean condition symptoms.