Wireless control systems for factory automation (FA) applications are subject to coexistence impairments, especially in license-free spectrum bands. Evaluating the coexistence impact requires the knowledge of appropriate characteristic parameters and the usage of a suitable simulation method. In this paper we propose an integral approach for the event-based simulation of wireless coexisting close-loop networked control systems (NCSs) for mutual impact evaluations based upon the integration of an ordinary differential equation resolving library within an event-based wireless network simulation framework. The approach is evaluated within a harsh FA scenario of two identical closed-loop NCS with two coexisting wireless technologies IEEE 802.11 and PNO WSAN-FA.