[corning_d3]

That sounds like the culprit to me, but it may not be the whole problem. It could have a leaking injector or something. Test the fuel pressure with the key on, engine off. It should be around 44-54 psi for both the 4.0 liter, and the 5.2 V-8. If the pressure bleeds down quickly after the key is shut off, there could be an injector not closing properly.