Maybe yall can shed some light on this also.
'99 Silverado 4x4, 5.3l, 3.73.
Problem: when driving at any speed with the cruise set at say 55 on level ground it drives perfect. but lets say I start to go up a hill and it needs to downshift and accelerate to maintaine speed. Just befor it shifts and the rpms raise the motor starts acting like it wants to die. It goes to stippin and stuttering pretty bad UNTIL it finally shifts and the rpms come up. Very strange.
History: I've owned the truck for like 3-4 months and all I have done to it is total fluid and filter changes(all mobil 1 synthetic and wix filters) (minus radiator) I have changed one spark plug becuase all the rest looked to be in pretty good shape, only changed the one becuse when I was taking it out I cracked it. I know I need to do plugs, wires, cap rotor sometime but I was going to wait till spring when work picked up. I also JUST had the fuel pump replaced under warranty. Both myself and my mechanic friend thought that the fuel pump might be whats causing the problem I stated. But as of today it's still doing it. We have yet to check fuel pressure after the regulator and we don't know about injectors. I'm more suspecting it's electrical now.. any way I could put my finger on this a little better?
Thanks Adair