VW Lupo Diesel Power Loss & High Fuel Consumption Fix

I had almost identical symptoms with my 2004 VW Polo diesel last year. Having some experience with diesel engines, I initially thought it might be related to the intake manifold or piston rings based on the power loss and increased fuel consumption. After a thorough inspection, the mechanic discovered the issue was actually connected to a previous repair. The crankshaft sensor had been replaced incorrectly during routine maintenance, causing improper timing and affecting cylinder pressure. Since this was a consequential error from their previous work, they fixed it at no cost. The repair involved: Proper reinstallation of the crankshaft sensor, Resetting the engine management system, Testing cylinder compression, Replacing damaged spark plugs caused by the timing issue Before suggesting more specific solutions, could you share: Current mileage on your Lupo? Any recent repairs or maintenance? Are you noticing any unusual exhaust smoke? Does the engine noise sound different? Have you scanned for error codes? These details would help determine if your symptoms match what I experienced or point to a different underlying issue.

Thanks for checking, my Lupo has 142398km on the clock. Though I had the timing belt replaced at 100000km, I can hear a slight whistling noise now when accelerating hard. This makes me wonder if the turbocharger might be failing. The last service was done 6 months ago. I did scan for codes which showed P0299, suggesting low boost pressure. Worth noting that black smoke occasionally comes from the exhaust under heavy acceleration.

Yes, those symptoms strongly align with turbocharger issues, I faced the same problem with my Lupo. The whistling noise combined with black smoke and the P0299 code points directly to turbocharger failure, just like in my case. When my turbocharger started failing, I initially thought it might be related to the fuel injectors or intake manifold, but the combination of symptoms was classic turbo wear. The black smoke occurs because the engine runs rich when the turbocharger isnt providing proper boost pressure. My repair involved: Complete turbocharger replacement, New intake gaskets, Cleaning the intake system, Oil change with turbo-specific oil The total repair cost was around 1200€, but it completely resolved the power loss and high fuel consumption. Make sure to address this soon, running with a failing turbocharger can lead to engine damage if metal particles from the worn turbo enter the system. Given your timing belt was done at the right interval and the head gasket seems fine, the turbocharger is the most likely culprit here. Consider having it checked by a diesel specialist who can properly diagnose the extent of turbo wear.

That helps a lot. Knowing my turbocharger is likely the root cause explains the symptoms I'm seeing. At my current mileage of 142398km, I guess turbo wear is not unexpected. I'll take it to a diesel specialist to confirm, but the whistling noise, black smoke, and P0299 code pointing to low boost pressure seem to match typical turbocharger failure symptoms. I appreciate the cost estimate of 1200€ for the full repair job, helps me budget for what's coming. Good to know the timing belt replacement I did earlier wasnt wasted money and that the head gasket isnt the issue. I'll make sure to get this looked at soon before any engine knocking or additional damage occurs from running with a failing turbo. Makes sense that the black smoke is from the engine running rich without proper boost pressure. I'll also ask about that turbo-specific oil you mentioned when I take it in. Thanks for sharing your experience, really helped narrow down the problem.