Time-difference-of-arrival (TDOA) localization systems estimate the difference in propagation delay between a target transmitter and pairs of receivers in order to locate the target. One important requirement is that the receiver nodes should be accurately time-synchronized, which is hard to achieve in practice without relying on cable-connected receivers. Over-the-air synchronization algorithms often rely on periodic messages from a master node, but due to clock drift, the rate of these messages needs to be high. In this paper, we propose a new synchronization algorithm that additionally exploits the carrier frequency offset (CFO) between the target node and the receiver nodes to reduce the rate of messages from the master node while maintaining good synchronization accuracy. Simulation results show the good performance of the proposed method, and preliminary experimental results show its feasibility on a hardware platform.