Experiments performed in a single-ended Q-machine examine the effect of a large-amplitude electrostatic lower hybrid wave on the dispersion of the current-driven ion acoustic instability. Nonlinear coupling of the modes provides a mechanism for suppression of the ion acoustic instability through a reduction in ion-acoustic mode phase velocity and an associated increase in ion Landau damping. An analysis which includes the effects of electron collisional or transit-time damping on the interaction is presented. This analysis demonstrates the resonant character of the interaction and allows quantitative evaluation of the lower hybrid power levels necessary for stabilization of the ion acoustic mode.