thanks everbody!
when i do clean my airbrush with thinner it would do the same thing.
would humidity have anything to do with it? because i airbrush outside. on the days i was airbrushing before it was humid and i had the sputtering spray issue. yesterday it wasn't humid at all and i used the airbrush, it didn't really sputter too much. it had a pretty consistent spray.
also, if i'm using a large amount of paint would that make it harder to siphon and possibly cause my problem?