I just had my 93 Aerostar 3.0 in for this same problem. My MAF sensor was plugged. Once cleaned, it now runs fine again.
Just had a rebuilt transmission still have no power going up hill
gravity
Its a Ford, that's the problem,
Generally when we are going up hill because of the gravity pull, more power is needed. So when traveling uphill more power is needed than downhill.
Because it is a Honda with a tiny motor.
if the vehicle is running properly(regular maintanance, tune-ups etc..), you have to downshift on inclines if your vehicle is standard shift. if automatic, disengage overdrive while going up hills.
shoot it
According to the 1997 Ford Aerostar Owner Guide : ( Motorcraft MERCON automatic transmission fluid is used as the power steering fluid )
You could either be in too high of gear or your (if manual)clutch might be going out.
Belt
Fuel Pump problem or clogged converter
If it is an automatic transmission going uphill it will downshift to a lower gear for more torque.