91 Cavalier no spark

I have a 91 Cav 2.2 w 120k miles. It started as an intermitent problem. Car would run for 45 minutes and then die. It had a very gasy smell to it. If you would try to restart it, it would just crank and crank, (turn over but not start.) Let it sit for a couple hours and it would start right back up and run fine for another 45 minutes. The time that the car stayed running decreased to the point that you could get it to start, put as soon as you put it in drive it would die.

I ran the diagnostic on it and got the codes for the 02 sensor and the MAT sensor. I replaced both of those and it ran fine for a day. The wife drove it this morning took it 2 blocks from home brought it back and it hasnt started since. Checked for spark at the spark plugs and there was none on all of them. Also checked for fuel supply and its definately getting fuel Someone said maybe a crankshaft sensor. I just didnt want to buy parts that wasnt going to fix the problem. Any ideas or things that could be checked would be greatly appreciated

Oh I also ran another diagnostics on it and the O2 sensor code still comes up