Macan Diesel Woes: Black Smoke & Power Loss Mystery

Hey there! I've had some experience with diesel engines. I actually faced a very similar issue with my 2016 Porsche Cayenne Diesel last year. The symptoms were almost identical, black smoke, power loss, and that annoying check engine light. Took it to my trusted workshop, and it turned out to be a faulty wiring harness connected to the fuel system. They replaced the wiring harness and connectors, cost me around 95€, and the car's been running perfectly since then. Before jumping to conclusions about the fuel pump (which would be way more expensive), I'd recommend getting the wiring checked first. What's your current mileage? And have you noticed if these issues happen more when the engine is cold or warm? This info would help me share more specific advice from my experience. Feel free to ask if you need more details!

Hi, thanks for sharing your experience! My mileage is currently at 136089 KM, and I just had my service done last month. Actually, I notice these issues more when the engine is warm, especially after driving for about 15-20 minutes. The jerking and power loss seem to get worse in stop-and-go traffic. You mentioning the wiring harness is really interesting, that's definitely a more affordable fix than replacing the fuel pump. Did you notice any specific warning signs before your wiring harness failed completely? I'm trying to figure out if I'm dealing with the same issue or if I should look elsewhere.

Hey again! Thanks for the follow-up. Yeah, I remember dealing with similar symptoms when my wiring harness was acting up. Actually, with my Cayenne, I noticed the issues were also worse when the engine was warm, just like you're experiencing. Before the wiring harness completely failed, I noticed that the problems were really inconsistent, some days the car would run fine, and others it would act up badly, especially in traffic. The jerking during acceleration was a major red flag for me too. One thing I didn't mention in my first reply, I also noticed that the problems would get worse on humid days. Looking back, that was probably because moisture was affecting the damaged wiring. My mileage was around 128000 KM when this happened, so we're in a similar range. I'd still recommend getting the wiring checked first before looking at the fuel pump. In my case, there was visible wear on some of the connectors, they looked a bit corroded. You might want to ask your mechanic to specifically check the wiring harness near the fuel system components. It's definitely worth ruling out before spending big money on a fuel pump replacement. Let me know what you find out, I'm curious if it turns out to be the same issue!

Hi everyone, Thanks so much for all the detailed input, especially about the wiring harness issue! You've given me some hope that this might not be as expensive as I feared. The similarity between your experience and mine is pretty striking, especially the part about the problems getting worse in humid conditions. Now that you mention it, I've noticed that pattern too but didn't connect the dots before. I've just called my mechanic and scheduled an appointment for tomorrow morning. I specifically asked them to check the wiring harness and connectors first, before jumping into any fuel pump diagnostics. They seemed to think it was a reasonable approach, given the symptoms. I'll definitely update this thread once I get the results. It would be great if it turns out to be just a wiring issue like in your case. Fingers crossed for that €95 bill rather than a fuel pump replacement! Thanks again for pointing me in the right direction!