The Finite Element Tearing and Interconnecting method for the Helmholtz equation is a recent nonoverlapping domain decomposition method for solving linear systems arising from the finite element discretization of Helmholtz problems in bounded domains. This method was validated on two-dimensional external problems with first-order absorbing boundary conditions. The purpose of this paper is to study the robustness and efficiency of iterative methods for the solution of the associated interface problem for three-dimensional interior problems arising from the automotive industry.