The drivers mirror on my '90 (square mirror) is shaking to the point where I can't see car behind me without giving myself a headache. The housing is tight but the actual mirror is vibrating in the housing. Any ideas on how to tighten the mechanism??
Not sure wheither you mean the door mirror or the interior mirror - I had
problems with both vibrating.
The interior mirror is held in place by a spring clip and it vibrates if the spring is a little slack. I managed to remove the mirror by sticking a small screwdriver in the top and releasing the clip and sliding it off. I then very carefully streached the spring a little - don't break it !!! - and replaced the mirror - Much Better.
The side mirror is held in plact by a rotating ring which you get at through a hole in the bottom of the mirror. Stick a screwdriver in a lever the ring around. If you go the right way you tighten the mirror, go the other way ad the glass falls out !!
I had to go to the garage and look at my car again. You had me confused when
you said you had two holes in the bottom of the mirror.
There are two holes but one should have a plug of some sort in it. There is one near the hinge but forget about that one.
There is one in the center - about halfway from the tip of the mirror to the door and this is the one you need.
Inside that hole there is the ring for tightening the mirror. It is about 5cm (2 inches) in diameter but only about 0.5cm in hight. Looking through the hole you see the bottom of the ring and with a screwdriver you can only lever it a few degrees each time.
The best way to imagine it is to think of it as the same as the lid of a jar lying on its side. You need to turn the "jar lid" by levering through the hole.
This is the plastic you see in the hole. The side of the ring has raised bits for to lever against. It should move easy - particularly if the mirror is already loose.
Let us know if you get it sorted.