And boy do I mean stupid. I am still learning this hobby but I suffered thru the identical situation you are. I had signals of 90 with 0% quality. It turns out that I was not on the satellite. In my short time working with this I have learned you will get signal no matter where you point the dish.
The quality issue is resolved (as long as the azimuth is correct) by adjusting the elevation. The first thing I found I was doing wrong was resolved by adjusting the elevation a hair at a time.
The next thing I found was I was trying to tune on a transponder that was not active. I found this by acident as I was flipping thru the different transponders. On
telstar 5 I kept flipping thru transponders then out of the blue the quality popped up.
I strongly recommend getting one of these cheapie
signal meters Sadoun has. You do your initial adjustments using a compass (I use radio shack digital compass) and one of these signal meters. Then fine tune it off the meter built into the receiver.