SQ7 TDI Power Loss and Stalling, Performance Issues

Having worked on diesel engines before with some hands-on experience, I faced almost identical symptoms with my 2018 Q7 TDI. The symptoms you describe match my experience perfectly, especially the power loss and rough idle. After scanning, my oxygen sensor readings were normal too, but the real issue was a faulty fuel injector. The intake manifold and throttle body were functioning correctly, but the fuel injection system was not delivering proper spray patterns, causing inconsistent air-fuel ratio. The repair involved: Complete diagnostic scan, Fuel injector replacement, System reprogramming, Test drive verification Total cost was 515 Euro for parts and labor. The repair solved all symptoms, no more jerking, normal power restored, and smooth idle. Before suggesting specific solutions, could you share: Current mileage, Any recent maintenance history, Whether symptoms appeared gradually or suddenly, Fuel consumption changes, Any unusual sounds or smoke from exhaust This information would help determine if your issue matches what I experienced and could save diagnostic time at the shop.

Thanks for sharing your experience. Just had my 42234 KM service done last month, but these symptoms started appearing suddenly after. The fuel injection system on these models can be tricky, but my initial testing with OBD showed normal readings. The catalytic converter seems to be functioning properly based on exhaust gas readings. The main concern is the stalling issue, which seems worse than what you experienced. Based on your repair list, I am considering having the fuel injectors checked, though the spray pattern test might reveal different results in my case.

Having gone through this myself, I can confirm that normal OBD readings dont always tell the full story. After seeing your update about the symptoms appearing right after service, this strongly reminds me of what happened with my Q7. The injector issue on mine initially showed normal readings too, but a more detailed spray pattern analysis revealed the problem. The stalling you mention being worse than my case suggests possible additional factors. In my followup testing, I discovered the fuel pressure regulator was also contributing to the inconsistent fuel injection patterns. The check engine light actually helped pinpoint this, it wasnt just the injectors, but the entire fuel delivery system needed inspection. The air-fuel ratio stayed within spec on basic tests, but under varying load conditions, the mixture was clearly off. Consider having the fuel pressure tested specifically, as this could explain the more severe stalling in your case. Some technical tips from my experience: Have all injectors tested individually, not just spray patterns, Check fuel pressure under different RPM ranges, Verify intake manifold pressure readings during cold starts, Monitor real-time fuel trim values during acceleration The sudden onset after service suggests possible fuel system contamination or disturbance during maintenance. This matches the pattern I encountered before the complete diagnosis revealed the full scope of the issue.

Using your perspective as the initial poster, here would be an appropriate conclusion: Really appreciate the detailed feedback. The suggestion about testing fuel pressure under different RPM ranges makes a lot of sense, especially since my stalling issues vary with engine load. Your experience with the fuel pressure regulator being a hidden culprit is particularly relevant. The check engine light in my case has been consistent, and the rich mixture symptoms match what you described. I will schedule a full diagnostic focusing on the fuel delivery system. The spray pattern analysis and individual injector testing seem crucial given the sudden onset after service. The mass airflow sensor readings might have been masking the real issue, similar to your case. Will make sure they check the intake manifold pressure during cold starts too, as that could explain the rough running condition. Looking at around 600 Euro for the complete diagnosis and potential injector work based on your repair costs. Thanks for helping narrow down the likely causes, this will definitely save time at the shop.