  The impact of quenched disorder on deterministic diffusion in chaotic
dynamical systems is studied. As a simple example, we consider piecewise linear
maps on the line. In computer simulations we find a complicated scenario of
multiple suppression and enhancement of normal diffusion under variation of the
perturbation strength. These results are explained by a theoretical argument
showing that the oscillations emerge as a direct consequence of the unperturbed
diffusion coefficient, which is known to be a fractal function of a control
parameter.
