I need help!!

had idle issues-
changed out:
plugs, rotor, cap, Mass airflow meter, idle control valve, air filter. '91 Monty running great. Then first cold snap here. Gets down to 20- now intermittent engine warning light and when it happens the idle is very rough, the engine vibrates more than usual, no power.
Then for no apparent reason, it solves for a short period of time. temp of engine has no bearing on anything.

Any thoughts...