majaflamme1
BMW Z4 Rough Idle Mystery: IAC Valve or Something Else?
Check engine light on
Fault stored
Stalling while idling
4 comment(s)
Hey! Thanks for sharing your experience! My issue with my Z4 sounds really similar to what you faced. I'm actually gonna get the intake system checked out first based on your advice rather than jumping straight to replacing the idle control valve. Just curious, do you remember roughly how much the intake cleaning service set you back? Also, have you had any similar problems crop up since the decarbonization was done? Cheers!
Hey again! Happy to update you! Yes, I just got my car back from the mechanic last week, and you won't believe it, it was exactly what I suspected from my previous experience. The intake was heavily contaminated, just like my M240i was. They did a complete cleaning and decarbonization job, and also found that the idle air control valve was indeed acting up, so they fixed that too. The total bill came to 425 €, worth every penny if you ask me! The car runs like a dream now, smooth as silk at idle. No more stalling, no more rough running, and the engine light is finally off. Such a relief! Since you asked about long-term results, after my first experience with the M240i, I haven't had any issues pop up again. Just make sure to use good quality fuel and maybe get the intake cleaned every 60k km or so as preventive maintenance. Let me know how yours turns out!
Thanks a lot for the detailed follow-up! Glad to hear you got your car sorted out. I actually just got back from my mechanic today. You were spot on, it was mainly carbon buildup causing the problems. Had the whole system cleaned and decarbonized. The bill was a bit steep but the difference in how the car runs is like night and day. No more rough idling or stalling issues. The mechanic was really thorough and showed me the gunk they cleaned out, pretty shocking how much carbon had built up in there! He also suggested regular maintenance to prevent it from happening again, just like you mentioned. Thanks again for pointing me in the right direction. Really saved me from unnecessarily replacing parts. Will definitely keep an eye on it and stick to quality fuel from now on. Take care!
Hey there! I had similar symptoms with my 2018 BMW M240i last spring. The rough idle and stalling turned out to be heavy carbon buildup in the intake manifold and intake valves. The check engine light was also on in my case. Had it inspected at the garage and the diagnosis revealed significant carbon deposits blocking proper airflow. The intake system needed thorough cleaning and decarbonization. It wasn't a quick fix, the mechanics had to remove the intake manifold and clean each valve individually. This was quite a serious issue that needed immediate attention to prevent further engine damage. After the service, the idle problems disappeared completely and the engine ran smooth again. Based on your symptoms, I'd suggest getting the intake system checked first before replacing parts. Carbon buildup is pretty common in direct injection engines at this mileage. Best of luck with the repair.