BMW 7 Series Rough Idle and Stalling, IAC Valve Issue?

Hey there! I have some experience working on cars and had a really similar issue with my 2006 BMW 5 series (also had a chance to work on the 3 series). The symptoms you're describing sound exactly like what I dealt with. My car was doing the same thing, rough idle, stalling, and that annoying check engine light. Took it to my regular workshop and turns out the intake was heavily contaminated, restricting proper airflow. Had it professionally cleaned and they also checked the sensors around it. Total bill was about 425 Euro, but it fixed the problem completely. Before jumping to conclusions about the idle air control valve, could you share: What error code you're getting? How many miles/kilometers on the engine? Has it been serviced regularly? This could help determine if you're dealing with the same issue I had. Let me know these details and I might be able to help more specifically.

Thanks for the detailed response! I'm at 16467 KM and just had my service done recently. The error code I'm getting is P0505. The symptoms match what you experienced, especially the stalling part, it's super annoying when stopping at lights. Good call on checking the intake first. I actually tried cleaning the throttle body myself but didn't notice much improvement. Interesting that you mention contamination, I'm wondering if I should get a professional cleaning done too. Did you notice any other warning signs before your intake got really bad? The price you mentioned for the fix seems reasonable if it solves the problem completely. Might have to bite the bullet and get it checked out professionally.

Hey again! Thanks for providing those details, knowing it's the P0505 code actually makes me even more confident about sharing my experience. You know what's funny, I also tried cleaning the throttle body myself first! And like you, didn't see much improvement. The main warning signs I noticed before things got really bad were slight power hesitation when accelerating and occasionally higher idle speeds than normal. But the stalling at lights was definitely the most annoying part, just like you're experiencing. Since we have pretty similar BMWs (mine's just a couple years newer), I really think you might be dealing with the same issue. The professional cleaning I got was way more thorough than what I could do at home, they used specialized cleaning equipment and actually had to remove some components to get proper access. One thing I learned from my experience, these symptoms can get worse pretty quickly if left unchecked. I'd definitely recommend getting it looked at soon. My mechanic mentioned that letting it go too long can sometimes lead to more expensive repairs down the line. By the way, 16467 KM is still pretty low mileage, which makes me think this is probably more about buildup than wear and tear. In my case, the cleaning sorted everything out and I haven't had any similar issues for over a year now. Let me know what you decide to do, I'm curious to hear if your fix ends up being similar to mine!

Thanks so much for all this information! You've definitely convinced me to get it professionally checked out. It's really reassuring to hear from someone who went through the exact same thing, especially with such a positive outcome. The fact that you haven't had issues for over a year after the cleaning is super encouraging. You're right about not wanting to let it get worse, I'm going to call my mechanic tomorrow and schedule an appointment. The stalling is driving me crazy anyway, and I'd rather deal with it now than risk bigger problems later. Really appreciate you taking the time to share your experience in such detail. The similarities between our situations and the matching error code P0505 make me feel much better about the whole thing. I'll update once I get it sorted out!