1999 Ford Explorer doesn't always idle from cold without revving the engine really high first.

Recently my 99 Explorer is intermittently failing to start. It turns over, immediately dies, then won't run at all unless I'm holding the throttle slightly. If I rev it really high, or hold the gas when I start it so it revs up right away then it idles fine and drives fine. If I've been driving it then it doesn't happen again unless I leave it for several hours. I've tried just low idling with the throttle barely down to warm up the engine and that doesn't help so I don't think it's a cold/hot issue. The only thing that fixes it is a powerful rev. There are no codes or anything. I'm really not sure about trim or engine details. This is just a beater that I picked up cheap off a friend.