XT4 Power Loss and Stalling: Rich Mixture Issues

I experienced something very similar with my 2018 XT5, and I have some experience working on cars as a hobby mechanic. The symptoms you describe match exactly what I encountered. In my case, the fuel injection system was the culprit. After diagnostic testing, they found a defective fuel injector that was causing uneven fuel distribution. The faulty injector was disrupting the proper air-fuel mixture, leading to the exact symptoms you mentioned, power loss, rough idle, and jerky acceleration. The repair involved: Complete diagnosis of the fuel injection system, Replacement of the defective injector, Testing the mass airflow sensor and throttle body (both were fine), Recalibration of the injection system Total cost came to 515€, including parts and labor. The repair completely resolved the issues, and the car has been running smoothly since. To help provide more specific advice, could you share: Current mileage on your XT4? When was your last fuel system service? Are you using regular or premium fuel? Have you noticed any unusual fuel consumption? Any other warning lights besides the check engine light? This information would help determine if your situation is similar to what I experienced.

Thanks for the detailed reply. At 85602 KM and my last service being just 2 weeks ago, I believe my issue might be different. After getting a diagnostic scan, it turned out my oxygen sensor was failing, causing incorrect air-fuel ratio readings. The intake manifold also had a small vacuum leak that was contributing to the problem. Both issues combined were causing the erratic behavior and check engine light. The mechanic mentioned these are relatively common issues that can mimic fuel injector problems. Getting both fixed plus a system recalibration should sort it out.

Thanks for the update on your XT4. Those oxygen sensor issues can definitely be tricky since they directly affect the air-fuel ratio calculations. The combination of a faulty O2 sensor and vacuum leak explains the symptoms perfectly. The mass airflow sensor readings were probably also affected by that vacuum leak in your intake manifold, leading the engine computer to make incorrect fuel injection adjustments. These components work together as a system, so one issue often cascades into multiple symptoms. Just to confirm, was the repair estimate reasonable compared to my injector replacement? While different problems, both involve maintaining proper fuel mixture. When I had my injector issue fixed, they also did a complete check of the oxygen sensors and intake system as part of the diagnostic process. Having those checked regularly helps prevent these kinds of problems from developing. Would you mind sharing the final repair cost once completed? It would help others with similar issues gauge expected expenses for oxygen sensor and manifold repairs.

Thanks everyone for the helpful information. I wanted to close the loop here, the final repair bill came to 380€ for replacing the oxygen sensor, fixing the intake manifold leak, and recalibrating the system. This was actually less than I expected given the symptoms. The check engine light is now off and the car runs perfectly smooth again. The catalytic converter readings are also back to normal according to the scan data. What I learned is that even small vacuum leaks in the intake manifold can cause significant drivability issues by throwing off the air-fuel ratio. The throttle body response is much better now too, no more hesitation or jerking during acceleration. For anyone facing similar symptoms, definitely get those oxygen sensors checked early. Waiting too long can lead to bigger problems down the line. My mechanic recommended getting the intake system inspected during regular service intervals to catch any developing vacuum leaks before they cause issues. This makes sense given how these small leaks can impact overall engine performance.