CPS is kinda a pain. Its in a spot on the back of the engine by the bell housing and its tough to get at. Its held in by a 5mm (im almost positive) hex head. Your best bet is to get the car up high and get at it from underneath. The reason its hard is that you can't really get more than a hand up there to pull it out, which depending on how long yours has been in there, it could be covered w/ gunk and tough. In the end, I just had my benz mechanic take care of it.

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87 300E
202k on the clock