I have a 2000 Dodge Ram 1500 v6, that we recently replaced the fuel pump. It ran fine for about 400 miles after that, then would start but not stay running unless the gas pedal was pressed. We cleaned the air filter, and ran 100% gas though it, along with some seafoam injector cleaner, and it seemed to be working fine. Running great, for well over 1500 miles. This morning when I went down to start the truck, it did it again. Not wanting to run without pressing on the gas. What could be causing this? I know its not bad gas...

 

IAC motor on the back of the throttle body.

Pull the throttle body, remove the IAC motor, clean the pintle, and the passages in the TB really well. Disconnect the battery for a few minutes after you put it all back together.

If that doesn't help, replace the IAC motor.

 

Agreed, Pull the throttle body and CLEAN IT OUT... Carbon build up can prevent it from doing what it needs to do