it won't keep running

here is my problem. when i start my car it cranks but it shuts right back off, if i put my foot on the gas a little it will keep running as soon as i take my foot off the gas it shuts off again. can anyone help me with this problem the car is a 96 gt

oh yeah after a holding my foot on the gas for a while the rpm's pick up and it runs fine until it sits for a while then it does this all over again. help!!!!!