Re: 2001 Expedition 4.6 hesitation
If there is no hesitation at higher rpm then you can rule out the fuel pump as a culprit. It sounds to me like you're experiencing engine 'lug', which happens at lower rpms. To test this out a bit better, drive at the same 55-60mph and keep the vehicle in third gear (not 4th or Over Drive) which should bring rpms around the 2600rpm mark. If the hesitation is still there then it rules out engine lug.
When was the last tune up performed, with new plugs? When you manage to do a fuel pressure test, get a compression test done as well. This will ensure that the engine isn't purposefully straining itself at 1500rpm. It takes a lot of torque to move around 3 tons of mass don't forget.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!