Starting Problem. Help!!!

I have a 1993 Chevy Cavalier with a 2.2 liter 4-cylinder engine. When I start the car in the morning, it starts fine, but if I park it somewhere and come back 20 minutes later, It doesn't start up the correct way. Upon starting the engine, the car sounds like it wants to stall out. The RPM's drop down, then the car recovers and idles fine. I sometimes have to press the accelerator in order to keep the engine from stalling out. I already changed the Idle Air Control valve Motor and cleaned out the throttle body. What else could be the problem? Maybe a spark problem? Thanks in advance.