The parity- and isospin-forbidden 0 decay from Ne*20(J=1+; T=1; Ex=13.482 MeV) to O16(g.s.) has been investigated by measurement of the longitudinal analyzing power Az of the reaction F19(p,0)16O around the 1+ resonance in Ne*20. With the data, the range for the expected interference effect has been reduced to Az=(15.07.6)×10-4 (68% c.l.), significantly smaller than a previous result. An analysis for the new data and those of related experiments has been performed to extract upper limits for the irregular 0 width 0PNC and the weak pion nucleon coupling constant f, being smaller than previous theoretical expectations. © 1990 The American Physical Society.