BMW Repair: BMW 328i Stalls When Cold, air intake hose, air intake system

Question
John,
I recently purchased a 328i with 70k miles and i have been having a problem with the car stalling.  What happens is when it is cold the car will idle at 1K rpm and then slowly dip down below 500 rpm.  Sometime the car will catch itself and rev back up to 1K rpm, but eventually it will drop below the 500 rpm and stall. This only happens when i am stopped and sitting idle for a little bit of time.  

Any ideas as to what is causing the problem and any things you would recommend replacing or fixing?

I am really stuck here and really don't know where to start.

Thanks in advance for your help.

Todd  

Answer
I'd check for air leaks in your air intake system.  Cracked hoses, loose clamps, etc.

Second, clean all the mechanisms/linkages through the air intake system.  The throttle valve, etc.

Third, there is a idle control valve.  It's connected to a smaller hose going to the larger air intake hose.  This may have a leak around it, or be dirty enough to cause problems.