BMW M4 Losing Power? PCV Valve Could Be the Culprit

Hey! I have some experience working on BMWs. Had a similar issue with my 2013 M3 last year. Those symptoms sound exactly like what I dealt with, unusual power loss and fluctuating speed. Super annoying! Took it to my regular workshop and they diagnosed a faulty crankcase ventilation system. The repair including parts and labor came to about 360 Euro. Since then, the car has been running perfectly smooth. Before I share more specifics, what year is your M4 exactly and what's the mileage? Also, are you getting any specific error codes? This could help confirm if it's the same issue I had. Just a heads up, if you smell oil or notice excess oil consumption, that's another typical sign of CCV failure in these engines. Let me know the details and I'll try to help further!

Thanks for the feedback! My M4 was serviced just last month at 88758 KM, and yeah, I'm getting a rough idle and can smell oil occasionally. The error code is P0171 (System Too Lean). I was hoping it wouldn't be the CCV, but those repair costs don't sound too bad actually. Did you also experience a slight hesitation during acceleration? Just trying to make sure I'm dealing with the same issue before booking it in for repairs.

Hey again! Yes, I definitely experienced that hesitation during acceleration with my M3, it was super frustrating, especially when trying to merge onto highways. The symptoms you're describing are exactly what I dealt with, right down to the P0171 code and rough idle. The oil smell and the recent servicing timing are also really similar to my situation. I actually had my car serviced about 6 weeks before these issues started showing up. Looking at your mileage (mine was around 85,000 km when it happened), it's pretty much the same timeline when these CCVs tend to start failing on these engines. One thing I didn't mention in my first reply, I initially tried to ignore it for a couple of weeks, but the hesitation got progressively worse, and the idle became really unstable, especially when the engine was warm. Don't make the same mistake I did by waiting! The repair was pretty straightforward at my regular shop. They had the parts in stock and the car was ready the same day. Since the fix, the acceleration is smooth again, no more oil smell, and the engine light hasn't come back on. Given all these matching symptoms, I'd say you're definitely dealing with a CCV issue. Better to get it sorted sooner rather than later!

Thanks so much for the detailed response! Really appreciate you sharing your experience, especially about how it got worse when you waited. I'll definitely book it in this week then, don't want to risk any further issues. Great to hear it can be fixed in a day, and good to know the symptoms match up exactly with what you experienced. I was worried it might be something more serious! Will update once it's fixed. Thanks again for all your help!