I have had a bit of a shake at idle for a short while now. After removing the distributor cap I noticed that nearly all the contacts are badly pitted and rusty in nature. I attempted to clean them up with a wire brush, with little success. It appears the contacts are now below the level of the plastic that supports each one where to rotor contacts it. I also cleaned the rotor with a bit of sandpaper. I still have the skake at idle. At higher revs I notice no shake, of course, and no loss of power or performance. I did replace the plugs, not the wires. Plugs are gapped at .032". Car is an 89 420SEL with 161,000 miles. Should I replace the distributor cap and rotor? Is it possible that all my sanding and brushing has made the situation worse via wider gaps? Any help will be appreciated.

If the cap and rotor are showing this much wear, you should replace. I would have the engine put on a scope to see if any of the resistor tips are out as well.

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