BMW 4 Series Rough Idle & Stalling, IAC Valve Issue?

Hey there! I had a somewhat similar issue with my 2013 BMW 3 series (also had a 5 series before). I have some experience working on cars, but mainly basic maintenance stuff. When my car showed those exact symptoms, rough idle, stalling, and fluctuating RPMs, it turned out to be heavy carbon buildup in the intake. My trusted mechanic did a thorough inspection and cleaning of the intake system. The whole thing cost me around 425 Euro, but it fixed the problem completely. The car's been running smoothly since then. Could you share your mileage and maintenance history? Also, have you noticed any other symptoms like drop in power or increased fuel consumption? This info would help determine if you're dealing with the same issue.

Thanks for sharing your experience! My odometer is at 196565 KM and I just had the regular service done last month. Actually, now that you mention it, I have noticed slightly higher fuel consumption lately, but didn't connect the dots until now. The carbon buildup theory makes a lot of sense, especially since I haven't had the intake system cleaned before. Will definitely get this checked out by my mechanic. The cost seems reasonable if it fixes the problem. Beats having to replace parts unnecessarily!

Hey again! Yeah, those symptoms you're describing sound exactly like what I dealt with. After reading about your mileage and fuel consumption issues, I'm even more convinced it's the carbon buildup, just like what happened with my BMW. My car had around 180000 KM when I faced the same problem. The increased fuel consumption was actually one of the first signs I noticed too, but like you, I didn't make the connection initially. The cleaning really made a huge difference, my fuel economy went back to normal and all those annoying idle issues disappeared. Quick tip from my experience: I started using a higher grade fuel after the cleaning, and it seems to help prevent the carbon from building up as quickly. Been about 18 months since the cleaning, and my car's still running like a charm. If your regular service didn't include an intake cleaning, that's probably your issue right there. Trust me, once you get it cleaned, you'll notice the difference immediately. My car felt like new afterward, no more stalling, smooth idle, and better fuel economy. Keep us posted on how it goes!

Thanks everyone for the helpful responses! Honestly, this makes me feel much better about the whole situation. After hearing about your experiences, especially with such similar symptoms at comparable mileage, I'm pretty confident it's the carbon buildup issue. I just called my mechanic and scheduled an appointment for next week to get the intake system cleaned. I'll definitely follow your advice about using higher grade fuel afterward too, seems like a smart preventive measure. It's such a relief to know it's likely not something more serious or expensive. Really appreciate all the input and practical advice! I'll update the thread once I get it sorted out to let you know if this fixed my issues. Thanks again for taking the time to help out a fellow BMW owner!