my car stalls when the engine warms up,why?

vacuum leaks. The key is, idles OK when cold, stalls when warm. Idle is directly related to vacuum. Double check all vacuum lines. Tighten all loose bolts, especially intake manifold, throttle body, etc. I use a squirt bottle with water, spray seams and hoses, etc when idling. When you hit the leak, the water temporarily seals it; engine perks up, smooths out for a few seconds. Cheap and easy troubleshooting method.