1995 Geo Metro Geo Metro 1995 WON'T STAY IDLING

I have a question about my Geo Metro 1995 4-cylinder standard. Whenever I start it up, I have to put my foot on the accelerator to keep it idling and if I let my foot off, it dies. It is a continuous pattern. It started with stalling out and hesitating at stop signs and stop lights and continued to get worse. I have replaced these parts so far: Fuel Pump, Fuel Filter, Distributor cap, Spark Plugs, Oil Filter and Oil change, New Battery. I need to know what is going on, I can't figure it out. Please help. Thank you.