BMW Z4 Water Sensor Woes, CEL and Rough Running

I had a similar issue with my 2016 BMW M240i last month. Initially thought it was more serious, but turned out to be a faulty connection at the coolant temperature sensor. The symptoms were identical, rough running and check engine light. Took it to the garage where they found corroded pins on the sensor connector and some debris around the wiring harness. They cleaned the connection points, replaced the sensor and connector assembly since they were pretty worn. Not a major repair, but definitely needed professional attention to prevent potential engine management issues. The job took about 2 hours total. Would recommend getting it checked soon, these sensors are crucial for proper fuel mixture and engine timing. Running too long with a faulty sensor can lead to poor fuel economy and potentially bigger problems. My car runs smooth now, no more check engine lights or rough running since the fix.

Hey, thanks for sharing your experience! Glad to hear you got it sorted. I actually went through something very similar with my Z4 last year. It's quite reassuring to know I'm not the only one who's dealt with this sensor drama. Quick question, do you remember roughly how much you ended up paying for the repair? Also, has everything been running smoothly since then, or have you noticed any other quirks pop up? Just trying to get an idea of what I might be looking at cost-wise and whether I should be prepared for any follow-up issues. You never know with these things!

Hey there! Yes, I remember the exact cost since I just got it fixed a few weeks ago, it came to 95 € total. They found the issue was just a dodgy cable connection to the water sensor, much simpler than I initially feared. I'm happy to report that since getting it fixed, my M240i has been running like a dream, no more check engine lights or any other issues. The rough running completely disappeared as soon as they sorted that connection. Honestly, it was such a relief that it turned out to be something relatively straightforward and not too expensive. You know how these things go, you always worry it's going to be something major, but sometimes it's just a simple fix. My mechanic actually showed me the corroded connection they found, and it was pretty obvious once they pointed it out. The car's been perfect since then, smooth running, no warning lights, nothing. If your symptoms are similar to what I experienced, you might be looking at the same kind of straightforward fix. Worth every penny for the peace of mind!

Thanks for all that info! Just wanted to update you on what happened with my Z4. I bit the bullet and took it to a mechanic yesterday. Turns out you were spot on, it was just a sensor issue, but slightly different from yours. The water pump sensor had corroded and needed replacing. The whole thing cost me 120 € and took about three hours to fix. The mechanic was actually really decent, showed me the old part and explained everything. He even cleaned up some gunk around the sensor housing while he was at it. Took it for a test drive afterward, and what a difference! The engine's running super smooth now, no more check engine light, and that annoying rough idle is completely gone. Should've done this weeks ago instead of worrying about it. Feels good to have it sorted. Really appreciate everyone's help and advice on this, saved me from stressing about potentially bigger problems. Time to enjoy driving again!