1990 Plymouth Acclaim

4 cylinder no upshift could be cheap repair but probably not. Although throttle pressure and the cable that controls it help determine upshifts and downshifts the kickdown band must apply and hold for a 1-2 upshift to occur. If the apply servo has a sealing or mechanical problem it can be repaired in the vehicle. So could a valve body replacement. I would say that the chance for an in vehicle repair without removing the transmission as 70 per cent.