1998 Ford Explorer engine will not start?

A few weeks ago i bought a 1998 explorer 4.0L. The seller said the o2 sensors were bad, the rig ran very rough, but no engine light on. After my own test i found the TPS to be bad and replaced it. It ran much better and the check engine light came on, the next day it would not start. It's got spark fires on ether and dies. Noid test showed injectors not working. So i replaced the CPS and it ran for one day now will not start. Got 38 psi on fuel pressure. MAF is good. What am i missing? could the PCM be bad? Help