It seems I have to adjust my IAC valve twice a year, once in the spring and once when the weather cools off in the fall.
Found the Thermac valve on air cleaner broken and actuator (motor) leaking on one of my troopers.
A three wire heated O2 sensor helps some also.
JOY in Paradise

3 90 Trooper V-6's, 5 speed, 4.3L TBI, 31" BFG AT's, Fender Flairs, Bored intake, 1.6 roller rockers, MSD Coil, Jacobs Omni ignition. Heavy duty torsion bars, Rancho 9000 Shocks CAN'T SPELL, TO OLD TO LEARN, GOD BLESS YOU IF YOU CAN.