Fox Diesel Power Loss After Mechanic Service Fix

Had the exact same symptoms on my Polo 2010 TDI. The check engine light came on and the car showed similar behavior, power loss, especially during acceleration, and very uneven running. The mass air flow sensor cleaning rarely solves injector-related issues. In my case, one of the fuel injectors was indeed defective. The diagnostic showed incorrect spray patterns and inconsistent fuel delivery. When fuel injectors fail, they often cause misfiring, which explains the jerking sensation you described. This typically happens due to carbon buildup or electrical issues within the injector itself. This turned out to be a serious issue requiring immediate attention. Left unfixed, faulty injectors can cause additional engine damage and increased fuel consumption. The repair involved replacing two fuel injectors that failed the pressure test, plus cleaning the throttle body since it had carbon deposits from the poor combustion. The oxygen sensor readings were also off due to the improper fuel mixture, but this corrected itself after the injector replacement. These symptoms are very typical for injector failure on TDI engines from that generation. Recommend getting a proper diagnostic focusing specifically on the injection system.

Thanks for sharing your experience. The fuel injector replacement really seems like the most likely cause based on those symptoms. The air-fuel ratio issues you mentioned match exactly what I experienced with my VW. The jerking and power loss went away completely after fixing it. Did you remember roughly how much the injector replacement cost? Also curious if youve had any other problems since the repair or if it fully resolved everything? In my case the EGR valve started acting up a few months later but not sure if it was related.

Just got the repair bill last week, it came to 515€ for replacing the faulty injector. The mechanic confirmed the engine was running too lean before, causing those power issues you mentioned. Since fixing the injector, the fuel mixture is perfect now and performance is back to normal. The repair completely solved the jerking and power loss issues. The oxygen sensor readings normalized right after, showing the engine is getting the correct fuel mixture now. The catalytic converter efficiency also improved once the proper air-fuel ratio was restored. Have not experienced any problems since the fix 3 months ago. The throttle response is smooth, no check engine light, and fuel economy is actually better than before. Unlike your EGR valve situation, everything else has stayed working properly. Getting the injection system fixed early probably prevented damage to other components. The mass air flow sensor they cleaned during your previous visit likely wasnt the root cause, its common for mechanics to try that first since its cheaper, but injection problems usually need actual parts replacement to properly resolve.

I took your advice and went back to the mechanic yesterday. The diagnostic confirmed what you suspected, a faulty fuel injector was causing all those problems. After checking the fuel pressure and spray patterns, they found one injector was completely clogged and another was starting to fail. The total repair came to 890€ for replacing both fuel injectors and doing a thorough fuel system cleaning. They also checked the throttle body and EGR valve while they were at it, but those components tested fine. The difference is like night and day. No more check engine light, the engine runs smooth as silk, and that annoying jerking during acceleration is completely gone. The mechanic showed me the old injectors and you could clearly see the carbon buildup that was disrupting the fuel spray. Honestly wish I had known about the injector issue before wasting money on that mass air flow sensor cleaning during my first visit. But at least its fixed now and running perfectly. Thanks again for pointing me in the right direction with this.