Could be oxygen sensors (located in the exhaust manifolds), water in gas, stopped up injectors, loose air hoses. Does it happen when its cold, hot, turning, been idleing for a while, in traffic, or going down the interstate? need more info. My 4.3 ran like this for a while then it began dying randomly and would not restart for 15 minutes or longer, turned out to be the ignition module (a.k.a. "the black bannana") it's inside the distributor, this won't be the case for you if you have C.O.P (Coil Over Plug) or H.E.I. (High Energy Ignition) mines 8 years older than yours I don't know what your engine runs.