My black 95 GTS is having trouble cranking. Every once in a while it when you try to crank it it won't turn over. If you leave it alone and let it sit for 20-30 minutes it cranks right up. Just recently while I was driving it the RPM's cut out and it wouldn't respond to the throttle. The check engine light came on and then everything kicked back in and she ran fine. My mechanic replaced the fuel pump, the O2 censors, and the mass air meter and told me it was fixed but obviously it isn't. Does anyone have any ideas?

haha