BMW 1 Series Diesel Issues: Rough Idle & Performance Drop

Hey there! I had something very similar with my 2013 BMW 3 Series diesel. I've got some experience working on cars, though I usually leave the complex stuff to the pros. Those symptoms sound exactly like what I dealt with. Initially thought it was something major, but turned out to be a loose connector to the knock sensor, basically a bad connection. Took it to my regular workshop and they diagnosed it pretty quickly. The fix was straightforward, they replaced the wiring and connector, cost me around 95 Euro. The relief when everything went back to normal! No more check engine light, smooth power delivery, and fuel consumption went back to normal. What's your exact engine variant? Would help to know that to see if it's the same setup as mine. Also, have you scanned for error codes? Would give us a better idea if we're dealing with the same issue.

Thanks for sharing your experience! My engine is a 2.0L diesel (N47 engine). I just had my service last week actually, but these issues started right after. Currently at 22471 KM and getting worried about these symptoms. Haven't scanned it yet, but planning to do that tomorrow. Good to know yours was just a wiring issue, gives me hope it's not something major. Did you notice any specific sounds or vibrations with your knock sensor problem? Mine seems especially rough during cold starts.

Hey again! Oh same engine as mine, the N47 2.0L diesel. That's quite interesting that it started right after the service. You know what? When you mentioned the cold starts, it really rings a bell, I had that exact same roughness during cold starts before I got mine fixed. In my case, I noticed this sort of irregular vibration at idle, especially in the morning. It would sometimes smooth out once warmed up, but not always. The throttle response was super inconsistent too, sometimes it would hesitate for a second before responding. Since you just had a service, might be worth checking if they disconnected anything around the sensor area during maintenance. Sometimes these connectors can be a bit finicky if they're not seated properly. Mine actually started acting up after an oil change, turned out the mechanic had accidentally knocked the wiring loose while working on something else. Definitely get those codes read, that's what really confirmed it for me. Keep me posted on what you find out! The good news is that if it is the knock sensor or wiring like mine was, it's a relatively simple fix. Your mileage is still pretty low too, so I wouldn't stress too much about it being anything major.

Thanks so much for all that detail, it's incredibly helpful! You've actually made me feel a lot better about the whole situation. The symptoms you described are spot on, especially that hesitation with the throttle response and the vibration at idle. I'll definitely check with the workshop about whether they worked around that area during the service. Just got back from getting the codes read, and guess what? It is pointing towards the knock sensor circuit! The mechanic had a look and spotted a partially disconnected wire, looks like it might've been knocked loose during the service, just like in your case. They're ordering the new connector just to be safe, but said it should be a pretty straightforward fix. Really appreciate you taking the time to share your experience. It saved me a lot of worry about potentially bigger issues. Will let you know how it goes after they fix it!