84 944 runs rough when cold and sometimes wont hold idle
 

a while ago my 84 944 started running really rough while it was at idle and would sometimes die, when i drove it it would cut out really bad and sometimes die as well if i didnt keep the rpms up, but once it gets fully warmed up it does fine. i have recently went to college and when i let it sit for a month itll run a lot better but by the end of the weekend it will be just as bad, any suggestions?..