All right, I got a 91, with 220K. bought it 2 months ago, the guy before me was not the best in taking care of it. This happened once before. I just got back from a 220 mile trip. When I have been idling for about 15-20 minutes or if traffic is very slow (maybe on long non stop driving), my truck begins to lose power and hesitate. It begins jerking and surging when I give it gas. When I take off from a stop, it completely siezes for a second then takes off, (with not much power). If I let the enginge cool off and rest, it will start up and drive perfectly again. The two things I am thinking it is: One is the tranny. The reason I though of this is because, sometimes it will rev up and the RPM will rise, but the truck will not go forward. But I don't think this will account for all of the loss of power or the surging. But today, my truck was running fine, until I gave it gas to pass someone, then it started surging and losing power again. It almost didn't make it home, but after it cooled down, it started driving fine again. I have checked the fluid, and it is full and the fluid looks good, but I have no idea how old it is. I have been planning to change the fluid, but have not done it yet. The other thing is maybe a vapour lock. that would explaing the surging and lack of power. But I just did the whole seafoam thing in my gas and intake, (throught the pcv valve). So there shouldn't be any water vapour in there to cause it to lock up. I think it has to do with some sort of heat related thing, but not sure what? Any Ideas?