BMW Z3 Cold Start Nightmare: Engine Control Mysteries

I had a similar issue with my 2004 BMW Z4 last winter. The symptoms were exactly like yours, tough starts and sometimes no start at all in cold weather. Took it to the garage and turns out the battery cable connections were badly corroded and loose. The terminals weren't making proper contact, which caused voltage drops during starting. The mechanic cleaned both terminals, replaced the corroded connectors, and properly tightened everything. It wasn't a major repair but definitely needed professional attention since it could've led to more serious electrical problems if left unchecked. The car's been starting perfectly since then, even in cold weather. From what you're describing, I'd check the battery connections first before assuming it's an engine control issue. These older BMWs are known for developing corrosion at the battery terminals. Might save you some time and money to start there.

Thanks for sharing that! Really helpful to know it was just the battery connections in your case. Mine's fixed now and working great after dealing with similar issues. Do you remember roughly how much the repair ended up costing you? Also curious if you've had any other starting problems since they fixed those corroded terminals? My Z3's been running fine after the fix, but always good to know what to watch out for with these older BMWs.

Hey again! Glad to hear you got your Z3 sorted out! Yep, I remember the repair cost clearly, it was 155 Euro for cleaning and replacing those corroded battery connections. Pretty reasonable considering how much hassle it was causing. Since getting that fixed, my Z4's been starting like a champ, haven't had a single engine control malfunction light or starting issue. Been about a year and a half now, and she's purring like a kitten, even on those chilly mornings. These old BMWs can be quirky with their electrical systems, but once you get the connections sorted properly, they're usually pretty reliable. Just keep an eye on those battery terminals every now and then, maybe give them a visual check during oil changes. If you start seeing any white or green crusty stuff building up, that's your early warning sign. But honestly, if they did a proper job with the new connections, you shouldn't have any issues for quite a while.

Thanks so much for that price info and the follow-up tips! I actually just got back from my mechanic today. They charged me 180 Euro for a similar fix, cleaned up the corroded connections and replaced some worn-out parts. The funny thing is, they found the exact same issue you mentioned with the battery terminals. There was this nasty green buildup that was causing all the trouble. The mechanic I found was great, really took the time to explain everything and even showed me what to look out for in the future. Such a relief after my previous bad experience! The car's starting perfectly now, and I've learned my lesson about regular maintenance checks. Honestly, I feel a bit silly for thinking it was a major engine control problem when it turned out to be something relatively simple. Really appreciate everyone's help on this, saved me from spending way more at the dealer!