1991 Ford Explorer hard to start

Hi Scribbledcanvas, my truck thier is no O2 sensors anymore. Its already condemned when I buy it. Yesterday I try to start and it was start when I shift into neutral and sometimes it start also in park but need to move the shifter up & down. Then I go to the parts store to buy the transmission range sensor, but I take the old one with me to compare with the brandnew one. My truck is 1997 model but the partsman told me that my transmission range sensor is for 1993 model, before I buy this truck the owner told me that they replace the transmission. Or maybe I have PCM problem.