after fill up, engine won't stay running

this is a new one for me, and I could not find a previous thread.



After filling, the engine will not stay running. It hunts between 300 and 1300 rpm, and will eventually die. It needs a bit of throttle to stay running, and will go fine after being put in drive and going a quarter mile.



I do not think it is over topped, the gas pump is in the auto mode. Car starts and idles fine once it gets passed the problem from filling.



I'm guessing something in the charcoal canister/vapor hoses/purge valve system? It doesn't throw any codes. Any ideas?



'99 323i automatic.



Thanks for the thoughts.