  We make use of a subtraction procedure, introduced to overcome
double--counting problems in beyond--mean--field theories, in the second
random--phase--approximation (SRPA) for the first time. This procedure
guarantees the stability of SRPA (so that all excitation energies are real). We
show that the method fits perfectly into nuclear density--functional theory. We
illustrate applications to the monopole and quadrupole response and to
low--lying $0^+$ and $2^+$ states in the nucleus $^{16}$O. We show that the
subtraction procedure leads to: (i) results that are weakly cutoff dependent;
(ii) a considerable reduction of the SRPA downwards shift with respect to the
random--phase approximation (RPA) spectra (systematically found in all previous
applications). This implementation of the SRPA model will allow a reliable
analysis of the effects of 2 particle--2 hole configurations ($2p2h$) on the
excitation spectra of medium--mass and heavy nuclei.
