Z3 Stalling Mystery: Limp Mode & Tank Valve Clues

Had the exact same symptoms on my 2005 BMW Z4 last year. Initially thought it was the tank ventilation valve too, but turned out the vacuum hoses were completely clogged with carbon buildup. The mechanic showed me how the hoses were basically restricted to pinhole-size openings. The car would stall at stoplights and go into limp mode out of nowhere, super frustrating. These symptoms got worse over about two weeks before I got it fixed. It was a serious issue that needed immediate attention since it affected engine performance and could've led to bigger problems. The fix involved replacing several vacuum hoses and cleaning the entire ventilation system. They also found a cracked breather hose while doing the work. Since getting it fixed, no more stalling or limp mode issues. My suggestion would be to have a good mechanic check the vacuum system first before replacing more expensive components. The symptoms you're describing are classic signs of vacuum/ventilation issues in these models.

Thanks for sharing your experience! The vacuum hose issue you mentioned sounds exactly like what I'm dealing with. I'm really glad you pointed this out, was leaning towards replacing the whole valve but checking the hoses first makes way more sense. Quick question, do you remember roughly how much you paid for the repair? Also, has everything been running smoothly since then, or have you noticed any other issues pop up?

Hey there! Happy to follow up about the Z4 repair. Yeah, I paid about 175€ for the whole job, mainly labor costs for cleaning and replacing those clogged hoses. Honestly, it was money well spent given how much trouble those blocked lines were causing. The car's been running like a dream since the fix! That tank ventilation valve that I was so worried about? Turned out it was working perfectly fine, it was just those gunked-up hoses causing all the drama. No more embarrassing stalls at idle, and the limp mode hasn't shown up since. The engine's running smooth as butter now. Just a heads up, while they were in there, they gave the whole ventilation system a good clean too, which probably helped prevent any similar issues from coming back. Been about a year now and haven't had a single problem with it. If your symptoms are matching what I went through, definitely get those hoses checked first. No point throwing money at expensive parts if it's just a clogged line causing the trouble.

Thanks a ton for the detailed follow-up! You've convinced me to bite the bullet and get it checked out. Actually just got back from a new mechanic I found, took your advice and had them look at the hoses first. Sure enough, they were completely gunked up, just like you described! The repair was pretty reasonable too, paid around 200 for the whole job, including cleaning and replacing some of the worst hoses. They even showed me the old ones, couldn't believe how clogged they were! Took it for a test drive afterward and what a difference, no more stalling, no more limp mode, and the engine's running super smooth now. Really glad I asked here before spending a fortune replacing parts that weren't actually broken. Thanks again for steering me in the right direction, saved me both time and money! Will definitely keep an eye on the ventilation system from now on to avoid any repeat issues.