BMW 4 Series: Multiple Engine Issues and Rough Performance

Hey there! I had some experience with similar issues on my 2012 BMW 3 Series (gas). I have some basic car maintenance experience, mostly doing simple stuff like oil changes and filters. The symptoms you described sound exactly like what I dealt with. Mine also had that annoying hissing noise and rough idle. Turned out it was a cracked intake hose, pretty common issue actually. Took it to my regular workshop, and they spotted the leak during a smoke test. Total repair was about 100 Euro, and it fixed all those issues, the poor acceleration, high fuel consumption, everything. Could you share your engine type and mileage? That would help narrow things down since different BMW engines can have slightly different common failure points. Also, have you had any recent work done on the engine?

Thanks for sharing your experience! I've got the same symptoms with my 4 Series at 167469 KM. Haven't done any major work recently besides the regular service last month. That's really helpful to know about the intake hose, sounds spot on with what I'm experiencing. Did you notice if your fuel consumption went back to normal right after the fix? Mine's drinking fuel like crazy right now and I'm hoping it's just this issue. Definitely gonna get that smoke test done to check for leaks.

Oh yeah, I've been there! After I got my 3 Series fixed, the fuel consumption dropped back to normal almost immediately, like night and day difference. It was such a relief because I was really getting tired of those frequent fuel stops. Just to add to what I mentioned before, when my mechanic did the smoke test, they actually found two issues: the cracked intake hose I told you about, and a loose clamp near the throttle body that was also causing some leakage. The whole repair took maybe a couple of hours, and honestly, it was worth every penny. The fuel consumption improvement was the first thing I noticed, but what really made me happy was how smooth the car ran afterward. No more jerking during acceleration, that annoying hissing sound disappeared completely, and the idle settled down to that smooth BMW purr we all love. Given your mileage, it's definitely worth checking those hoses and connections. These parts tend to wear out around that point, and the regular service might not have caught it if they weren't specifically looking for leaks. Keep us posted on what you find out, always good to share these experiences with other BMW owners!

This is exactly what I needed to hear! Really appreciate you taking the time to give such detailed info about your experience. I'm gonna call my mechanic tomorrow and specifically ask for a smoke test to check those intake hoses and connections. It's such a relief to know this might be a relatively simple fix and not something major with the engine. The fact that your fuel consumption went back to normal right away is super encouraging, that's been one of my biggest headaches with this whole situation. The loose clamp tip is great too, I'll make sure they check all the connections around the throttle body. Thanks again for sharing your experience, it's helped me feel much more confident about getting this sorted out. I'll definitely update once I get it checked out.