BMW: 93 BMW V12 rough idle, check engine light, bmw v12, bmw engines

Question
Josh,

Recently, my 1993 BMW 850 idles uneven (+,- 100rpm) after cold start, check engine light comes on. When operating temp is reached, then RPM's surge and fall until engine stalls.
If I slightly depress the accelerator, the engine hesitates as if it's going to stall, then revs higher.
Tried on-board self diagnostic, no codes flashing.

Started up and ran perfect, no check engine light, a couple of days ago.
I can tell you that this situation used to always occur after heavy rains and heavy moisture
in the air. Then, after the car warms up for 15 minutes, the symptoms would disappear completely
and not return until high moisture and rain appear.
I know moisture used to be a culprit, now the symptoms just described occur regardless.

Much appreciated,

Brenden

Answer
Brenden,
 Unfortunately I have absolutely NO experience with the V12 BMW Engines.  I know the 8-series has a notoriously complex electronics system.  It is basically 2 inline-6 engines that share a crank.  So it runs like a car with 2 engines under the hood.

 I would suggest finding a qualified BMW mechanic to work on this car.

 Good luck,
 Josh