VW Up Fuel Injection Faults: Stalling and Power Loss Fix

As someone with moderate experience working on VWs, I had a very similar issue with my 2016 VW Polo last year. The symptoms you describe match exactly what I experienced, poor idle, reduced power, and constant check engine light related to the fuel injection system. After multiple diagnostic tests, my mechanic found that the high pressure fuel pump was failing, causing irregular fuel pressure and affecting the entire fuel injection system. The repair ended up costing 1510€ including parts and labor. Since the fix, the car has been running perfectly with no fuel efficiency issues or engine misfires. The fuel regulator was initially suspected, but car sensors indicated it was actually the pump causing the problem. Its worth having a proper diagnostic scan to pinpoint the exact issue, as multiple components in the fuel delivery system can cause similar symptoms. Before suggesting more specific solutions, could you share: Current mileage on your Up, Whether you notice any specific situations when the problems are worse, If the car sensors show any specific error codes, Any recent maintenance history related to the fuel system This information would help determine if your issue matches what I experienced with my Polo or if it might be something different.

Last service was done at 70000km, currently showing 82555km on the clock. The issues definitely get worse when the engine is warm and especially during stop-and-go traffic. Car sensors are showing error code P0171 which points to a lean fuel mixture condition. I checked the fuel injection pressure with a gauge and its showing inconsistent readings, fluctuating between 35-45 PSI at idle. The check engine light is now constant rather than intermittent as it was initially. Tried cleaning the mass airflow sensor but that didnt help resolve the lean condition. Starting to think this might be more serious than just a dirty sensor or minor fuel system issue. Would the high pressure fuel pump replacement cost be similar in my case? Any other diagnostic steps you recommend before committing to such an expensive repair?

Based on the error code P0171 and your pressure readings, this really does mirror the issues I had with my Polo. Those fluctuating fuel pressure numbers are a classic sign of a failing high pressure fuel pump, which aligns with the lean fuel mixture warning. The repair cost should be comparable, expect around 1400-1600€ for parts and labor. However, before committing to the pump replacement, I recommend having these additional checks done: 1. Test the fuel regulator under load conditions 2. Inspect fuel lines for potential vacuum leaks 3. Check fuel injector spray patterns In my case, the mechanics initial fuel injection system diagnosis suggested multiple potential issues, but running these additional tests confirmed the pump was the primary culprit. After the replacement, my fuel economy improved significantly and the engine performance returned to normal. Your mileage is very close to when my pump failed (around 80000km), which is a common interval for fuel system components to show wear. The warm engine symptoms you describe are particularly indicative of a pump issue rather than a regulator problem. Consider requesting a complete fuel system pressure test, this confirmed my diagnosis and might save you from replacing parts unnecessarily. The car maintenance history you shared suggests you keep up with regular service, so other components should still be in good condition.

Thanks for the detailed feedback. I decided to take my Up to a certified shop for a complete fuel system pressure test, definitely want to confirm the exact issue before spending 1500€ on a new pump. The symptoms matching your experience with fluctuating pressure and the P0171 code make me think youre right about the pump being the likely culprit. Ill have them check the fuel regulator, lines, and injector patterns too while theyre at it. Good to know the repair solved your fuel efficiency issues completely. The fact that our cars had similar mileage when the problems started is pretty telling. Will update once I get the test results and repair quote. Hoping its not more extensive than just the pump but at least I have a better idea what to expect cost-wise. The declining fuel economy and rough idle are getting worse so I want to get this resolved quickly before it potentially causes more damage to the fuel injection system.