  We study a $p$-Laplacian equation involving a parameter $\lambda$ and a
concave-convex nonlinearity containing a weight which can change sign. By using
the Nehari manifold and the fibering method, we show the existence of two
positive solutions on some interval $(0,\lambda^*+\varepsilon)$, where
$\lambda^*$ can be characterized variationally. We also study the asymptotic
behavior of solutions when $\lambda\downarrow 0$.
