what will cause the engine to shake while in park and it gets worse as you drive down the road
bad engine mounts/ worn ignition components
engine mounts could be a possibilty ... how ever to keep going on the ignition comment ... i had an odd jerking motion most of the time when in park and occasionally when driving that got progressively worse ... the simple fix was new plugs and wires ... that was a month ago and no problem since ... however if you pull the plugs and they are covered in oil you may need to replace your spark plug seals ...
These 2 guys nailed it on the head. I've had motor shake from both causes before. I'd check the front motor mount and ignition components too. Overall, at most a $45 fix I believe maybe even less.
Check the pasenger side motor mount (lower). I just replace it on my friends car and everything stop.
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