surging/check engine 318is

just got a '91 318is a month ago,and it was running well. today was the first cold weather test (15 degrees). she ran well out of the garage, but after being parked out in the cold she started surging (stalling at stops) - the "check engine" light goes on/off, and around 2000 rpm she seems to die down (like she's not getting fuel). only other thing i noticed is that the temp gauge never gets above 1/4 and that when cold the rpm's don't seem to kick up. any ideas?