Hello,
This may be something simple like a stuck EGR valve, but, there really is no telling without diagnostics - especially for the 7 series.
This is a "flagship" model, and the engineers who build these really pour a lot of technology into them, so the fault potential is endless.
I recommend using a good independent European auto technician/shop. They will see 7 series issues all the time.
Casey is right-- the 7 series has a "lot of engineering" in it -- it does sound like it's a "cold start issue" which is messing up the running of the car when it is warm -- think of the old days when we used to say the car needs a "choke" when it's cold -- the engine is richer with less air while cold so the engine can start -- when it's warm if this system is not operating correctly it can cause it not to start (i.e. possibly running too rich so it won't start).
The good news is all of this is now "computerized" in the ECU and we can put sensors and diagnostic tools to "check" the computer for operation and it will likely indicate exactly what is going on and we can then recommend a repair plan for you.
Can you come in to lawerenceville? We'd love to assist. That is a fine car and you will want it to run great!
Best,
MMW
