In this article, the kinetic energy distribution of atomic and molecular nitrogen ions is reported for two electron cyclotron resonance (ECR) sources. Methods to reproducibly tune the kinetic energy of ionic species from 3 eV to 35 eV have been developed in order to produce monoenergetic ion beams for the demanding requirements of selective energy epitaxy. This article also describes methods to avoid the discontinuous hysteretic transitions between stable ECR modes. The changes in the ion energy distribution resulting from these abrupt transitions are characterized.