A predictive schedule based energy efficient MAC protocol named as PSE 2 -MAC is proposed in this paper for asynchronous wireless sensor networks. Although the asynchronous MAC protocol offers better performance than that of synchronous MAC in terms of energy but infrequently it suffers from beacon collisions as well as idle listening problem. Although many researchers avoid discussion on beacon collision but it has a great impact on asynchronous MAC. For this reason, the authors in this paper have highlighted the beacon collision problem and proposed a possible solution with prominent results. Along with the solution, the authors have proposed a prominent technique to solve energy consumption issue caused by idle listening. The performance of the proposed protocol has been evaluated and the evaluation result shows that PSE2-MAC performs much better than conventional IEEE 802.15.4 protocol for managing the beacon collision. Also, the simulation results show minimal energy consumption due to idle listening. Thus, the proposed protocol helps to improve overall network performance and throughput.