surges while climbing a hill at same speed

Help? I have replaced spak plugs, wires, cap, button ,fuel filter and Fuel Pump.
I still have the same problem, no engine light is on.While traveling at the same speed ,climbing any type incline the vehicle surges 4 to 5 times and then will run fine. It may run fine for awhile, then it may do it again. Can any one help? Iam going to Tampa Flordia in May, and I don't want to be left stranded on the side of the road.

probably the Torque converter clutch engaging/disengaging. Touch the brake pedal slightly enough to raise your rpms and see if it still happens, putting the vehicle in third may help too