This used to happen in my '89 IROC as well. My issue was that when the key is turned to start the gauge does a test sweep
(I think that's what it is anyway) where it shoots up to max real quick, then back down... When it shot up, the needle would get caught up on the lip of the gauge
(you will probably be able to tell what I mean when you get the bezel, lens, and light reflector off).
But, anyway, I ended up bending the edge of the lip down a little where the needle would get caught up, and that worked fine for me. If you do decide to do it this way, just be careful with it. Make sure you have a good grip on the gauge and don't force it too much; don't want to pop the face off the gauge... I just used a pair of pliers on mine. Maybe put some tape on the end of the pliers to keep from scratching the gauge face.
The gauge itself comes out as one unit. If I remember correctly, you should be able to get a couple fingers behind the face of the gauge and just pull straight out. It has a couple studs that push into some metal contacts behind it.
Well, there you go. That how I did mine. Once you get the bezel and stuff off you will be able to see more of what's going on with it and maybe formulate your own idea of how to fix it. I also thought of gluing a little stop peg onto the gauge face, but decided against it 'cause of how fast the gauge moves during "the test sweep," I was worried it might break the needle... Anyway, sorry for the novel
. Hope it points you in the right direction.
I wish I would have thought of that... Definitely easier and less potential for breakage. Good idea. 
