Is it possible for a 91 style cavalier rim to leak air or am i just freaking out and have a bad tire?

probably, you could nic'd the rim and caused a small leak, or the tire could have a nail/screw/glass in it causing a leak, or the valve stem (there is a little metal pin inside) that could be loose. that happened to my car. i went to fill it w/ air and as soon as i took the air hose off i heard it coming out so i put the cover back on and went to my tire shop. they told me it comes loose sometimes and they took needle nose plyers and tightend it