Cayman's Rough Running: Knock Sensor or Something Worse?

Hi there! I have some experience with cars and had a similar issue with my '06 Boxster (also had a stint with a Cayman GT4). Sounds very familiar, I had almost identical symptoms. Turned out it was just a faulty sensor cable/plug connection. Got it fixed at my local Porsche specialist for about 95 Euro. The mechanic showed me that the cable was slightly damaged, causing those weird symptoms you're describing. Before jumping to conclusions though, could you share: Any error codes you're getting? When did these symptoms start? Has there been any recent work done on the car? This info would help pinpoint if you're dealing with the same issue I had. It was a pretty straightforward fix in my case, but better to be sure!

Thanks for sharing your experience! My symptoms started about two weeks ago, right after my latest service actually. I'm getting error code P0327, which points to the knock sensor circuit low input. Haven't done any other work on the car recently besides regular maintenance. I'm at 103638 KM, and it's been running like a dream until now. Interesting that you mention the cable, that would definitely be a less painful fix than replacing the whole sensor. Did your car also have fluctuating idle when this happened? Might try your mechanic if they're in my area!

Hey again! Yeah, you mentioning the P0327 code really rings a bell, that's exactly what I got with my Boxster. And yes, mine also had that annoying fluctuating idle, especially when the engine was warm. The timing of your symptoms starting after the service is interesting because that's pretty much what happened to me too. In my case, I'm pretty sure the cable got slightly pinched during the service work. These Porsche engines are pretty tight to work on, and it's easy to accidentally catch a wire when putting everything back together. When my mechanic traced the issue, he found a tiny nick in the insulation that was causing intermittent connection issues. My car's at 112,000 KM now and running smooth as silk after that fix. The symptoms disappeared completely once we sorted the cable issue. I'd definitely recommend getting someone to check the wiring before replacing the whole sensor, could save you a bunch of cash! BTW, if you want to check yourself first, the knock sensor wiring usually runs along the left side of the engine (when you're facing it). Sometimes you can spot visible damage if you look carefully with a flashlight. Just be careful poking around when the engine's hot! Let me know how it goes, always happy to share more details about my experience if you need them!

Thanks so much for the detailed follow-up! That's super helpful, especially about the cable potentially getting pinched during service, makes total sense since the timing matches up. I actually just grabbed a flashlight and checked the wiring like you suggested. While I couldn't spot anything obvious, I'm definitely going to have a pro take a closer look at the cables before jumping into replacing the sensor. Would you mind sharing where your mechanic is located? If they're not too far, I'd love to take it to someone who's already dealt with this exact issue. Really appreciate you taking the time to share your experience, it's given me hope this won't be as painful (or expensive) as I initially feared!