[Lemke20]

So I'll start with the history. 2008 335xi with around 110k or so. RB turbos, fbo, custom tune from Ken. All regular maintenance done, walnut blast not that long ago, spark plugs are still good, etc. Started when weather got cold and my car would start up super rough like it was trying to die and would sometimes clear up or not happen if I started the car over. This went from once a week to eventually every time I started it and rarely got it to go away. Then started getting mixture control codes and nothing to go off and eventually for O2 sensor codes a week ago. Changed them out and car was perfect for 2 days. Driving home from dinner with no problems and all of a sudden as I got to my neighborhood when I touched the gas the car would be hunting for power and jerky. Coasted home and didn't have any codes or lights. Then I started getting a coolant temperature sensor code and changed that out. No luck except the code going away (see pic for newest codes except coolant temperature codes didn't come back). Got the terminal codes and stuff and was being told it was my battery possibly. Swapped it with my buddies and still no change. Really out of ideas and want to try fixing it myself before going to the dealer Wednesday. Also, car runs too bad for me to be comfortable driving around to graph a log. Any input helps

[upshift_downshift]

Originally Posted by Lemke20

So I'll start with the history. 2008 335xi with around 110k or so. RB turbos, fbo, custom tune from Ken. All regular maintenance done, walnut blast not that long ago, spark plugs are still good, etc. Started when weather got cold and my car would start up super rough like it was trying to die and would sometimes clear up or not happen if I started the car over. This went from once a week to eventually every time I started it and rarely got it to go away. Then started getting mixture control codes and nothing to go off and eventually for O2 sensor codes a week ago. Changed them out and car was perfect for 2 days. Driving home from dinner with no problems and all of a sudden as I got to my neighborhood when I touched the gas the car would be hunting for power and jerky. Coasted home and didn't have any codes or lights. Then I started getting a coolant temperature sensor code and changed that out. No luck except the code going away (see pic for newest codes except coolant temperature codes didn't come back). Got the terminal codes and stuff and was being told it was my battery possibly. Swapped it with my buddies and still no change. Really out of ideas and want to try fixing it myself before going to the dealer Wednesday. Also, car runs too bad for me to be comfortable driving around to graph a log. Any input helps

It's probably your Intelligent Battery Sensor (IBS):

https://bimmerscan.com/bmw-intellige...ry-sensor-ibs/

Make sure all the blue connectors around the battery are plugged in. The shadow code for fuel pump also makes me think your HPFP is beginning to go.

[Lemke20]

Originally Posted by upshift_downshift

It's probably your Intelligent Battery Sensor (IBS):

https://bimmerscan.com/bmw-intellige...ry-sensor-ibs/

Make sure all the blue connectors around the battery are plugged in. The shadow code for fuel pump also makes me think your HPFP is beginning to go.

We made sure when we swapped the batteries. Would unhooking it and starting it possibly be a temporary fix to determine if that is the problem?

[335e92tx]

Several early cars have been identified with bad grounds. Start with checking the rear-deck ground and also hot connnection. Are they SOLID. Is there any corrosion at the mount point?

?

[JuniorB]

The ground cable is a major issue with these cars, as its exposed to the elements. Remove, clean all points of contact, and if you have any shred of doubt if it's no good, replace it. In this case, it dosent seem to be an issue, is sounds like a power relay issue. If it's intermittent, this is a good sign that power is being loss, and regained. There are so many of them in this car, and none of them are lifetime. Hold off on changing anymore sensors,the car will run with them on. Unless your seeing DME faults itself, I'd look for power to Ecu relays.

[JuniorB]

Also, look for water,,and corrosion in the Ecu box.

[Lemke20]

Turned out to just be ignition coils causing a small misfire but not throwing a code. thanks for the help everyone!

[JuniorB]

Imagine that, with no codes!