99 lesabre

my car will start and run but after about 3 or 4 minute it shuts off i can start it back up but only if i hold the gas petal down half way but as soon as i take my foot off the gas it shuts off

If you don't have a scanner, you need to take rthe car to a big box Auto Parts store & have it scanned for free. Once we have that info, we may be able to help; otherwise, we would be just throwing darts in the dark.