ok

...still working. Part arrived yesterday, more this weekend. Thanks again for help.

Well new idle control valve in there and unfortunately no change in behavior. Did go along pulling coil connections to see if I could change behavior, but sound I'm getting is slightly different so I will have to assume no misfire. Plus no codes for that.

Went to the dealer to pick a tech's brain. After giving him symptoms and codes he put into his computer and pulls up a service bulletin for three batches of wiring harnesses. Sent me home with numbers check against my own the Engine wiring harness. Sure enough I have 12517513548, one of these sets on my harness. I remain skeptical that this harness is at fault, though I realize their data points in that direction.

I am a stumped now. Next step I guess is to bring it to my local indy, give him the history and get his take. Up until this point I am the only one that has actually heard and experienced the stalling/misfiring.

Wiring harness looks like a lot of labor and 500 beans for the parts.

Thanks for reading and don't be shy about additional input.

Looks to me like either the harness problem or mass air flow sensor problem. With problems like this the multiplicative vaules set in the DME are usually pegged at 12%, so I swap with a known good MAF and drive it a few miles... if the multiplicatives start coming back to normal range you know you had a bad MAF. If that don't do it.... harness time. (since you fall within the bulletin range, you likely need that damn harness)

And FWIW I would use some MAF cleaner from autozone instead of WD40 on that MAF sensor... the oil film will fudge the readings and make you run more rich vs the cleaner that will remove the film and leave it perfectly dry with no residue.

I looked to this old post and noticed that you had exactly the same problem then me sometimes ago, the engine ran very well from full tank to 1/4, then very roughly and even stalled below 1/4. I spent a bit of time to find the cause! In the case that this is a similar cause, there is a small o-ring on the fuel tank, LHS, just where the pump is located. This non-Viton o-ring tends to crack with age due to unleaded fuel, so the pump sucks air instead of fuel when the fuel level is too low. As the fuel tank is in 2 parts, the fuel cannot be pumped from the RHS to the LHS. Go to real OEM parts and you will see the o-ring. Hope that this is the same problem, cost is about 2 USD!...

This is my new mechanics number, call him, give him the symptoms and see what he says,Owners name is Bill name of the shop is L&M Foreign Cars (718)451-9894, I went there last week and he's pretty legit, 2nd generation technician, opened the shop in 69,

Drive the car until the service engine light comes back on, scan it and tell me what the code it, It could be the wiring harness, but more likely is the mass airflow

Thanks for all of the help and the follow up BMWFiend, you were right all along with the Mass airflow sensor and replaced it yesterday. Bavarian Chariot is back on the road and I learned quite a bit.

Good luck out there until next time and thanks again.

No problem, glad I could help.