okay, so i just bought a 91 xlt 4.0 v6, replaced all the plugs and wires, and all the fluids. but here is the problem, when you first start it up it has a sputter, if you floor it it will go away, it does not sputter every time just every now and then, and some times it will sputter and cut off, and its got plenty of gas so thats not it, what could it be? has a sensor gone bad? also whats the average mpg of the 4.0??

thanks for all the help