We study the system LaxMnO3+/-z, in order to produce proper self-doping (Mn3+/Mn4+ ratio) by La vacancies only, in place of divalent substitution. The system is stable in the range 0.8 < x < 1.0, -0.05 < z < 0.05, with a rhombohedric structure, close to the orthorhombic one, but a mixed phase of both could also be present, We study the Ca substitution, as well as the Ni doping, in order to fix the Mn valence state. The system is ferromagnetic with T-c spanning from 200 to 300 K. depending on the doping level, with a saturation value approximate to 2.7 mu(B)/Mn atom. LaxMnO3+/-z present a metallic-insulator transition, and a magneto-resistance effect close to 75% at 200 K under an applied magnetic field of 9 T, with RT (300 K) value close to 50%.