At higher mileages, (125,000-150,000) the automatic transmission may not shift correctly. This can be caused by the throttle position sensor being out of adjustment or a shift solenoid needing to be replaced. Typically the transmission does not need to be completely overhauled.Google+
Car Problem Reports
Toyota Previa Automatic Transmission May Not Shift Correctly at High Mileages
Toyota Previa Problem
Drive Train Affected: RWD
Average Mileage: 152,750 mi (120,000 mi - 185,000 mi)
Visitor, 1991 Toyota Previa
my van wont shift gear
Visitor, 1992 Toyota Previa, RWD, 156,000 mi
This just started three days ago. It was running and shifting just fine one day and the next, it was having problems shifting, surging. I thought it was cap and rotor, but this may very well be it. I will investigate more tomorrow.
Visitor, 1991 Toyota Previa, 120,000 mi
car can't pick-up the speed. it's happen every morning when i drive to work.