Node cooperation is a basic requirement for the operation of Mobile Ad hoc Networks (MANETs). However, a user may misbehave due to several advantages resulting from noncooperation, the most obvious being power saving. As such, enforcing the cooperation among nodes becomes a very important issue. Several different approaches have been developed for non-cooperative MANETs. It is found that the proposed approaches have several concerns that prevent them from really enforcing the node cooperation in MANETs. In this paper, a new scheme to stimulate and enforce nodes cooperation in ad hoc environment is presented. The scheme applies various mechanisms to detect and exclude potential threats of selfish mobile nodes. Simulation results indicate that our scheme makes MANETs more robust against nodes' misbehaving and the system performance is enhanced many folds when compared to other existing schemes.