1991 300d, W124 260k

The accelerator pedal is sticking down (still accelerating after I let up on the pedal) for a few seconds after I floor it, then it comes back up. What could be causing this? Might it be old grease in the cable? (I think they have grease inside the cables, right?). Maybe I just need a new cable. It doesn't do it when accelerating normally; just if I need to get up a steep hill or something.

Or is it more likely to be the many ball and socket linkages in the engine compartment? I recently lubed those with some grease.

Thanks.