Manet is a collection of self-organizing mobile nodes participating in the network to forward packets for each other. However, some nodes in the network do not forward packets in order to save their energy. But these nodes make use of other nodes to forward their packets. Such unfair use of the network leads to degradation of its performance. So it is very important to detect such misbehaving nodes in the network. So in order to improve network performance we propose a scheme that is a combination of overhearing and acknowledgement based method to detect misbehaving nodes. The scheme is proposed to be built on top of DSR routing protocol.