Resonant pulse combustors, one of the deflagration-based pressure gain combustion devices, can significantly increase thermal efficiency in gas turbine engines. This experimental study investigates the stability characteristics of a newly designed actively valved resonant pulse combustor, capable of sustained operation and meaningful stagnation pressure gain. The resonant pulse combustor was fired with liquid gasoline fuel while ion and pressure sensors captured the temporally resolved heat release and chamber pressure. First, experimental results were used to demonstrate the general operating principle of the combustor. Then, the stability characteristics of the device were investigated through frequency domain analysis of the ion probe and pressure signal traces. A low frequency oscillation (also observed in steady flames and passively valved resonant pulse combustors), was observed as the device was brought near to its blowout limit. Finally, an index was defined to predict the stability characteristics of the resonant pulse combustor by quantifying the competition between low frequency oscillations and combustion-driven resonance. Experimental results demonstrated the ability of this index to provide early prediction of a blowout event for this device.