We present integral field data of the infrared luminous merger galaxy ESO 148-IG02 obtained from the ANU Wide Field Spectrograph (WiFeS). We apply AGN and shock models to investigate the relative contribution from star formation, shock excitation and AGN activity to the optical emission in this key merger stage. We find that ESO148-IG02 has a flat metallicity gradient, consistent with recent gas inflow. Using kinematic information we separate the line emission maps into a northern non-rotating star formation region with low velocity dispersion, and a southern rotating system with high velocity dispersion which is influenced by AGN activity. We show that the two overlapping galaxies can be separated using the kinematic information, demonstrating the power of integral field spectroscopy.