For prolonging network lifetime, several energy-efficient routing schemes were proposed in wireless sensor networks (WSNs). Directed Diffusion (DD), a data-centric routing paradigm, is one of these schemes. In this protocol, every node has ability with sensing, collecting, and storing event data. Also, the best transmission path, called reinforcement path, will be determined by using exploratory packet information in DD. Transmitting data via reinforcement path can avoid blind transmission, and ensure that event data can quickly reach the base station. However, most of DD-like protocols are concentrated on finding an optimal routing path for single-source data transmission environment, and the paradigm is difficult to recover its faulty path when some fault occurs. In this paper, an integrated routing protocol is proposed, termed as Source Coalition Directed Diffusion (SCDD), to study multi-source data transmissions in WSNs. SCDD can not only efficiently merge two nearby data flows to reduce network traffics and the number of packet collisions, but also effectively create a spare path for fault tolerant routing. The simulation results show that SCDD can achieve about 2%~14% by comparing with original DD scheme. The fault tolerant routing method of DD, REEP, can also be improved by cooperating with SCDD to achieve 4%~13% improvements.