VW Sharan Diesel: Fuel Mix Issues Causing Power Loss

Had a similar issue with my 2012 VW Touran diesel recently, and being someone with some basic car maintenance experience, I initially thought it might be related to the mass airflow sensor causing a rich mixture. Took it to my regular workshop after attempting basic diagnosis. They found a faulty injection valve that was causing irregular fuel delivery. The symptoms matched yours exactly, power loss, rough running, and that characteristic jerking during acceleration. The rich mixture was actually a result of the faulty injector not atomizing fuel properly. The total repair came to 515€, which included diagnostic time, parts, and labor. The fix made a dramatic difference in performance, smooth acceleration returned and the check engine light cleared immediately. Before suggesting specific fixes, it would help to know: Current mileage on your Sharan? Have you noticed any black smoke from the exhaust? Did the problems start suddenly or develop gradually? Any recent fuel system maintenance performed? The throttle body and oxygen sensor readings would also be helpful diagnostics to rule out other potential causes. This could help narrow down whether your issue is definitely injector-related or something else in the fuel system.

Last service was 2 months ago at 96200km. The black smoke started appearing from the exhaust about 2 weeks ago. The problems developed gradually over the past month, getting worse each week. The check engine light started flashing intermittently before staying on permanently. The throttle body was cleaned during the last service. The air-fuel ratio seems to be affected mainly during acceleration, which matches what you experienced. The fuel injection system has not had any maintenance beyond regular service intervals. I will get it checked at a workshop this week based on your experience. The symptoms being so similar gives me a good starting point for diagnosis. 515€ seems reasonable if it resolves these issues completely.

Based on your mileage and maintenance history, your symptoms strongly align with my experience. The gradual onset and black smoke are classic indicators of injection problems, just like I encountered. The mass airflow sensor readings on my Touran were initially misleading, suggesting a rich mixture issue when the root cause was the injector. Since your throttle body was recently cleaned, we can likely rule that out. The intermittent check engine light followed by constant illumination matches exactly what happened with my vehicle when the injector was failing. The fact that your air-fuel ratio issues occur mainly during acceleration is another matching indicator. The repair cost might vary slightly depending on labor rates, but the 515€ I paid included a full diagnostic check of the spark plugs and fuel system. Given that your symptoms developed over a similar timeframe to mine, getting it checked soon is wise to prevent potential damage to other components. One tip from my experience: have them check all injectors while they are at it. Sometimes when one fails, others might be showing early wear signs. This could save you from facing similar issues a few months down the road.

Thanks for sharing that extra detail about the service history and black smoke issue. The similarities with your injection valve problems make me feel more confident about getting this sorted. The progression of symptoms, especially that black smoke and worsening performance, matches what you described perfectly. Your point about checking all injectors makes sense. I will ask the workshop to inspect the complete fuel injection system. I understand how one faulty injector could lead to poor air-fuel ratio and cause the issues I am experiencing. The gradual decline in performance does suggest a failing component rather than a sudden fault. Going to book it in tomorrow, aiming to have the throttle body and injection system properly diagnosed. The 515€ repair cost gives me a good benchmark. Hope they can get it running smoothly again like they did with your vehicle. Really appreciate you sharing your experience, gives me a much clearer picture of what to expect. I will keep an eye on those check engine codes and any catalytic converter issues that might develop from running rich for this long. Better to get it fixed now before it causes more problems.