In Ad Hoc networks, node misbehaviors due to selfish or malicious reasons can significantly degrade the performance of ad hoc networks. Previously, we proposed a trust-based incentive model on a self-policing mechanism to make nodes evaluate the trust of their neighbor locally [1]. That approach can mitigate contamination by direct observation and the use of second-hand information available. However, one situation hasn’t been considered that the secondhand information can be spurious, which raises the questions of how to incorporate it in a safe way and whether to propagate it. In this study, we adopt a trust evaluation method with a trust scaling factor on that trust-based incentive model to relieve the influence of fake second-hand information on the accuracy of trust value. Performance by simulation reveals that in the case of existing malicious nodes, the enhanced trusted Dynamic Source Routing (ET-DSR) with proposed trust evaluation method performs better than T-DSR in terms of packet successful delivery ratio and mean number of packets dropped. Meanwhile, ET-DSR is more suitable for large scale networks than T-DSR due to the introduction of trust scaling factor.