I had the same problem with my 1991 ranger 3.0 back in 1992, it acted like a carbureted engine with a bad automatic choke, even though it's actually fuel injected. Once mine warmed up, it too ran just fine. My code scanner said the TPS (Throttle Position Sensor Voltage was low). I replaced it (on left side of throttle intake) & that fixed it.
1991 Ranger XLT 3.0 V-6, 5 speed Mazda R1, Long Bed
244,000 + miles