Rough idle then dies when at half a tank or below

[perx]

I have a 2011 bmw e92 m3 dct i took my cats and mufflers off after i done that i noticed my car will rough idle when stationary at a stop sign or stop light the rpm will bounce from 500 to 1k never passed 1k then it’ll drop close to 0 it’ll sound like it’s struggling whole care shakes then it’ll just die like a stall or something the only codes I have are P0056
And p0036 anyone know a fix for this track day is coming up and I wanna get this fixed asap

[spammysammich]

Did you re-use the crush gaskets at the xpipe to header junction? Did you double check the ground wire near the left side header connection to make sure it is in good shape? Are you absolutely sure you didn’t hurt the wiring harness or pins for the O2 sensor? You should be running a stage 2 tune for optimal performance running catless.

[perx]

Originally Posted by spammysammich

Did you re-use the crush gaskets at the xpipe to header junction? Did you double check the ground wire near the left side header connection to make sure it is in good shape? Are you absolutely sure you didn’t hurt the wiring harness or pins for the O2 sensor? You should be running a stage 2 tune for optimal performance running catless.

A tune could fix the issue? And yes I checked every gasket and o2 sensors seem but I also heard people tell me it could be my fuel vent valve

[spammysammich]

You may need a tune to keep those o2 sensor faults from popping up and the car running happy. You will kill rear o2 sensors without tuning for being catless. Exhaust leaks at the crush gasket also kill o2 sensors. Also did you add a forward x-pipe, placing the crossover point more towards the front of the car? That can cause drivability issues.

You’ve said it didn’t start playing up until you modded the car. Do more research before throwing more parts at it. As others have mentioned it could also be the fuel breather valves. Search this forum and see if the symptoms match.

[perx]

Originally Posted by spammysammich

You may need a tune to keep those o2 sensor faults from popping up and the car running happy. You will kill rear o2 sensors without tuning for being catless. Also did you add a forward x-pipe, placing the crossover point more towards the front of the car? That can cause drivability issues.

You’ve said it didn’t start playing up until you modded the car. Do more research before throwing more parts at it. As others have mentioned it could also be the fuel breather valves. Search this forum and see if the symptoms match.

Noted I’ll definitely look around forums idk if this could have an affect to it but I did remove the mufflers and that’s when the stalling and loss of power started

[spammysammich]

There are ground straps at the rear of the car on the muffler hangers that actually need to be retained and connected. Did you keep them? More than one person has reported very odd behavior of the car with those grounds broken or missing.

[spammysammich]

Also, please get a hold of a scan tool that can read BMW specific codes. Generic p codes aren’t very helpful for remote diagnosing things. Foxwell 510 or whatever has been recommended by many others if you can’t do ISTA

[perx]

Originally Posted by spammysammich

There are ground straps at the rear of the car on the muffler hangers that actually need to be retained and connected. Did you keep them? More than one person has reported very odd behavior of the car with those grounds broken or missing.

I’ll have to double check has it wasn’t me that did the job. And I have a code scanner that’s why I’m so confused bc only codes I’m getting are o2 sensors and that’s it it’s just really stressful but a lot of my friends say it could be a vaccum leak as well

[bradzx]

check fuel breather valve or replace

[BimmerRob08]

Originally Posted by bradzx

check fuel breather valve or replace

Yes try this. My understanding is if it’s failing, your fuel tank won’t breath and ends up losing fuel pressure. I supposed a fuel pressure gauge might tell you the pressure at different tank levels and see if you notice a difference. I don’t know where on the fuel rail we can connect it but I’ve done this on an older explorer that has the port on the fuel rail. But we should also be able to read live data on the scanner tools, just need to know what normal pressure is supposed to be. I’m sure someone can better answer this here.

[perx]

Originally Posted by bradzx

check fuel breather valve or replace

I did and my fuel breather valve was perfectly fine the problem was my battery replaced it and problem went away hopefully 🤞

[LJ35extraordinaire]

Any update? has it happened again lately?

[Soden82]

Originally Posted by spammysammich

There are ground straps at the rear of the car on the muffler hangers that actually need to be retained and connected. Did you keep them? More than one person has reported very odd behavior of the car with those grounds broken or missing.

What’s wild is that when I received my car from the PO, both ground straps on the muffler were not attached. Somehow did not have any electrical issues as a result.

[RocketyMan]

Originally Posted by Soden82

What’s wild is that when I received my car from the PO, both ground straps on the muffler were not attached. Somehow did not have any electrical issues as a result.

Because there's one last ground strap on the oil pan to the body of the car.

There's 3 total ground straps. Two on the exhaust and one on the oil pan.