[shorod]

Sounds like your Explorer is in need of a tune up, and have the vacuum lines looked over. You may be experiencing a misfire under load due to worn spark plugs, arcing spark plug wires, restricted fuel filter, weak fuel pump, dirty fuel injectors, restricted air filter, etc.

As part of a tune up, I would expect the plugs to be checked and or replaced, the plug wires to be inspected and/or replaced, the fuel filter to be changed, and a bottle of fuel injector cleaner added to the fuel tank. The air filter should also be inspected and probably replaced. This seems like a good place to start based on your descriptions.

Other items to check: coolant temperature sensor, oxygen sensors, fuel pressure, mass airflow sensor, throttle position sensor, EGR valve.

-Rod