It sounds like the choke plate is sticking shut. You can remove the air box to gain entry to the choke assembly. Manualy close the the ckoke to see if it stays closed and does not release. if it stays stuck, remove the screws holding the solenoid, insert a thin flat washer between the spring and solenoid. This will keep the choke plate from binding on the plastic. This will keep the choke plate from closing to where it will bind. Have not seen a problem where it gets below zero, and units running on propane.
Thanks scoot....will talk this over with the service tech.