In wireless ad hoc networks, fair allocation of bandwidth among different TCP flows is one of the critical problems that affect the performance of the entire system. This paper proposes a fairness mechanism - Adaptive_Pause. Adaptive_Pause is a simple and distributed scheme that only needs little communication and processing overhead. Each node monitors the occupation of the channel due to its emissions and dynamically determines whether it should pause a time interval in order to avoid channel capture. Comparing to other passive schemes in which a node limits its transmission when it receives congestion indication from its neighbors, the proposed scheme is more effective and requires less overhead. Simulation result validated our analysis result and gave the optimal parameter setting. Both analytic and simulation results show that Adaptive_Pause scheme can improve the TCP fairness.