[rstep]

Hello and welcome to German Engineering, specifically BMW. To preface my slew of issues, I drive a 2015 BMW 328i, with 69xxx miles on the car. I had purchased the car with 49xxx miles on it. The car is manual, with the M-Sport package, whilst the car was with me, there were frequent oil changes done every 3-5k miles, and the car was never pushed to the limit, rather most of the time it was babied. Up until about about a week ago the car was an absolute dream, never ever gave me any issues not even a code, however on my drive back home from the gym I noticed the car struggling to accelerate in 5th gear ~2.3k rpm to 2.5k rpm, with the revs dropping before picking back up again. I began to try to replicate the issue, and was able to in 3rd, 4th, 5th, and occasionally 6th in 3rd and 4th gear it was very noticeable at ~3k rpm. I will attach a link to a youtube video of what I'm mentioning. I plugged in my obd reader, and got a reading on my boost of the turbo thinking that may be the issue. I noticed during the hiccup my turbo would go from pushing 13 psi of boost, to 7-9 psi, then slowly climb back up. (please see the attached video) I thought it may have been the gas/ water in the gas. So I poured dry gas, hoping that would fix my issue, and unfortunately it did nothing at all. I figured I would use all my gas up, go to a different top tier station as opposed to my Mobil, however I got to half a tank left to go, and then the dreaded electrical issue began. Yesterday on my drive to my university ~20 miles away, the car threw a message on I-Drive stating Battery Charging Malfunction, I thought my alternator had gone bad, so I went home and bought a new alternator to replace the current one (hasn't been done). I thought little of it, drove it home with the message constantly coming and going, with the same OBD reader I could tell my battery was throwing the message the moment it went under 11.6 voltage, and then in acceleration would charge up to 13.3 voltage, then go away. Today when I drove it to school, I got a new message from the battery (white), stating Battery Discharge while stopped. I figured the alternator should come in the next couple of days and my issues should leave with it. Now on the drive home right before I pulled into the drive thankfully, I lost Power Steering, and ABS. I thought of the serpentine belt however the belt looks to be in good condition, the only issue I think I may have is the bottom pulley, looks to be a bit off course, almost like off centered, I made a video again if that will help with the understanding. Has anyone had an issue like this, if so how did you fix it? Did you take it to a shop and what did they do/ what was the cost? Any advice is much appreciated!

Links
Acceleration:

Serpentine Belt: https://youtube.com/shorts/rFHNYIBYWe8

Cheers to BMWs

[rstep]

Update for those who are interested. I plugged the battery into a charger last night, and kept it on charge for about 16 hours. After taking it off the voltage measured 13.2. After waiting another 45 minutes the new voltage was 12.6.

[Billfitz]

That's more drop than you'd expect in 45 minutes. You may have a parasitic current drain. Google it. See what it does overnight.

[rstep]

New update, I pulled out my OBD scanner from the port, and the drainage has slowed to a halt. However after driving the car the battery still lost voltage. I ended up changing the alternator and serpentine belt. For the time being my voltage loss issue is (knock on wood) gone. Along with the Christmas tree of electrical issues. The random power loss/ turbo boost loss is still there. I’m still hoping it’s a bad gas issue, I have a third of a tank left, and I should use that up sometime in the next 7 days or so.

[MaverickCruise]

I don't think this problem has anything to do with the battery, it's something else. Such as air intake system, VANOS, timing chain, etc.

[rstep]

Originally Posted by MaverickCruise

I don't think this problem has anything to do with the battery, it's something else. Such as air intake system, VANOS, timing chain, etc.

I hope not, but that being said. I haven’t noticed a difference in idle/misfiring in lower rpms, which would lead me to believe it’s not the vanos. My car is a late production 2015, meaning it came with the updated chain without the common faults, and the symptoms are similar to vanos. The are intake could be the issue, off my naked eye I haven’t noticed any hissing, however it definitely has to do with air/gas/timing in higher rpms.

[Billfitz]

FWIW change the chain tensioner. Having the new chain may prevent a problem with it, but all the evidence indicates that it was the tensioner at fault. It was upgrade in late 2016.

[rstep]

Another update/ Quick Recap

- New Alternator
- Resolved my electrical issues
- Ran the car to E, hoping the rpm issue was bad gas it wasn’t
- Will put new coils and spark plugs this weekend, hoping that is the issue
I’ll provide another update after the install

Thanks for the suggestions, will look to try them once I get the cheaper stuff out of the way