We report our results on the experimental total cross sections (TCSs) for positron scattering from the isoelectronic molecules N2, CO and C2H2. Where possible, for each species, comparison is made between the present results and those from earlier measurements and calculations. The agreement between the present and earlier experimental results, within the overall uncertainties on the data, is typically satisfactory for energies greater than about 8 eV, but is only marginal at lower positron impact energies. While N2, CO and C2H2 possess 14 electrons each, we find significant differences in the magnitudes of their respective TCSs and subtle differences in the energy dependence of these TCSs. These details are discussed in depth in this paper.