98 Taurus SE / Sometimes starts, sometimes doesn't

My wife's 98 Taurus runs great! Bought it with 40,000 and now have 110,000 on it and it's never been in the shop. I do the maint. and it has been great.

The problem is sometimes it just doesn't start. It turns over fine but doesn't start. Let it sit for a half hour and bang... it starts fine. Happens about once a month. Very frustrating especially when we are on our way somewhere important and it desides to act up like this.

any suggestions..........

While cranking the engine, try depressing the accelerator about 3/4. If it starts you may want to check out the IAC, (idle air control valve). I had this problem too. The car would crank just fine, let it set for a while and then it would start right off. I don't know why but, one day I stepped on the gas peddle when this was happening and it started right up. After a couple of times of experencing this I decided to pop the hood when it wouldn't start and tap on the IAC. After doing that the car started. I repeated this a couple of times and then went out and bought a new IAC. No more problem. I guess the IAC was sticking in the closed position and not letting air into the engine while trying to start.????

Good luck!