VW Polo TDI: Black Smoke + Power Loss Points to PCV

I encountered a very similar issue with my 2006 VW Golf TDI. The symptoms you describe match exactly what I experienced, especially the smoke during acceleration and rough idle behavior. After some initial DIY checks, I had a certified workshop diagnose the problem. They confirmed a defective crankcase ventilation system, which was causing oil to be pulled into the intake, leading to those emissions issues and the power loss you mentioned. The repair involved replacing the complete crankcase ventilation valve assembly and cleaning the intake manifold. Total cost was 360€ including parts and labor. Since the fix, both idle stability and emissions have returned to normal, and the engine runs like new. Before suggesting specific solutions, could you share: Current mileage, Any recent maintenance history, Whether you notice any oil consumption, If there are any other warning lights besides check engine, Whether the smoke is black, blue, or white This information would help determine if your issue is identical to what I experienced and whether you might need additional repairs beyond the ventilation system. Regular maintenance in this area prevents many valve-related issues, but when leaks develop, they need prompt attention to avoid more serious engine problems.

Thanks for the detailed response. Just checked my service history, last maintenance was 2 months ago at 19750km. Since then the issue started appearing gradually. No other warning lights present, and the smoke appears bluish. Oil consumption seems normal based on my dipstick checks. The ventilation valve symptoms you described match exactly what I am experiencing. The idle gets particularly unstable when the engine is warm. Really helpful to know the repair costs and specific components involved, gives me a clear idea what to expect at the workshop.

Thanks for providing those details. The bluish smoke and unstable idle when warm, combined with your timing of symptoms after the last service, strongly suggests we are dealing with the same crankcase ventilation valve malfunction I experienced. In my case, the bluish smoke intensified over about 3 weeks before I got it fixed. The valve leak was allowing oil vapor to enter the intake system, causing both the smoke and the power issues. The unstable idle you mentioned is particularly telling, mine also got worse with engine temperature. The repair on my Golf was straightforward, but waiting too long led to some oil residue buildup that needed extra cleaning. Getting it addressed early helps avoid this additional work. Since your mileage is relatively low and maintenance is current, you likely just need the valve assembly replacement like I did. The smoke and idle issues should resolve completely once fixed. Given the identical symptoms, expect repair costs to be similar to what I paid at around 360€. Remember to mention the gradual onset of symptoms to the workshop, this information helped pinpoint the valve issue in my case versus other potential causes of smoke during acceleration.

Thanks for that excellent information about your similar case. Your symptoms with the Golf TDI definitely help confirm what I'm dealing with. Since my service history is recent and mileage relatively low, focusing on the ventilation valve makes perfect sense. The gradual development of symptoms in my case matches yours, starting with minor power loss and progressing to the current state with more noticeable smoke during acceleration and that unstable idle. The leak seems to be getting worse, especially when the engine is warm. I will schedule a repair appointment this week before the malfunction causes any additional problems or oil residue buildup in the intake system. The 360€ cost estimate gives me a solid reference point for the work. Based on your experience, fixing this early should prevent more extensive repairs later. Really appreciate the detailed comparison that helped identify this specific issue. Having someone confirm the same progression of symptoms definitely makes me more confident about the diagnosis and repair approach.