VW Lupo Diesel: Power Loss and Rough Idle Fix Tips

Had almost the exact same issue with my 2002 VW Polo diesel last year. Being moderately experienced with car repairs, I first thought it was related to the mass air flow sensor causing an incorrect air-fuel ratio. After the check engine light came on and experiencing similar symptoms, rough idle, jerking during acceleration, and significant power loss, I took it to my regular workshop. Their diagnostic revealed a faulty fuel injector that was causing uneven fuel delivery to the engine. The complete repair included: Testing all injection valves, Replacing the defective injector, Recalibrating the fuel delivery system, Clearing the engine codes Total cost came to 515€, including parts and labor. The repair resolved all symptoms, and the engine has been running smoothly since. To provide more specific advice about your Lupo: What diagnostic codes is it showing? Have you noticed any unusual fuel consumption or exhaust smoke? These details would help determine if your issue is similar to what I experienced with the injection system. Also, when was the last time you had routine maintenance done on items like fuel filter or intake manifold cleaning? These can sometimes contribute to similar symptoms.

Thanks for sharing your experience. After reading multiple responses, I checked my fuel consumption logs from my last service at 20505km, and I noticed the car has been using about 15% more fuel than usual. The diagnostic showed error code P0171, suggesting a lean condition. The exhaust has a slight grey tint, especially during cold starts. Based on the responses, I am leaning towards getting the EGR valve and oxygen sensor checked first, since they are common failure points that can cause these symptoms. The catalytic converter also shows signs of reduced efficiency according to the diagnostic readings. I will update once I get more concrete findings from the mechanic.

Thanks for the additional details. The P0171 code combined with increased fuel consumption definitely aligns with my experience. After dealing with my injector issues on my Polo, I learned these symptoms often point to multiple interconnected problems. The oxygen sensor was actually the root cause in my case, even though the symptoms initially pointed to the injectors. The faulty sensor was sending incorrect readings, causing the ECU to adjust the air-fuel ratio incorrectly. This led to the lean condition and eventually damaged one injector. Some key points from my repair journey: The oxygen sensor replacement cost 180€, The lean condition had started affecting the catalytic converter, The intake manifold needed cleaning due to carbon buildup If your mechanic is checking the EGR valve and oxygen sensor, ask them to inspect the intake manifold for deposits as well. These carbon deposits can restrict airflow and contribute to the lean condition youre experiencing. The grey exhaust smoke during cold starts particularly matches what I dealt with before the repair. This often indicates the engine is compensating for incorrect air-fuel mixture readings.

Thanks for all the helpful information. I just got back from the mechanic and wanted to close the loop on my Lupo issues. You were right about the interconnected problems. The diagnostic confirmed both a failing oxygen sensor and a clogged EGR valve. The mass air flow sensor readings were also slightly off, affecting the air-fuel ratio calculations. The final repair involved: Replacing the oxygen sensor: 175€, Cleaning the EGR valve: 120€, Cleaning the intake manifold: 90€, New spark plugs as preventive maintenance: 65€ Total came to 450€ including labor. After the repairs, the engine idles smoothly again and the power has returned to normal. Fuel consumption is back to standard levels and the check engine light is off. The mechanic mentioned the catalytic converter is showing early signs of wear but should be good for another year if the air-fuel ratio stays properly regulated with the new parts.