2000 nissan sentra runs well on warm up, stalls in

I actually had this problem on my 97 sentra, its the air idle control valve. when your car is idling with your foot off the pedal, the throttle plate is closed, so this little valve opens up to allow air to detour around the closed throttle plate so your car can continue to run, when you give it gas the plate opens so your engine can increase revs.

after awhile the idle air control valve gets dirty with carbon buildup and eventually makes the valve stick so no air can pass through it which is why the car will stall when it attempts to idle. all it needs is a good clean. its very easy to do, just get some brake cleaner and a toothpick or q-tip or some other small brush.

locating this valve is a bit tricky, yours is a 2000 model mines a 97 so it wont be in the same location as mine, but what your looking for is a little cylinder type thing somewhere near the intake with an electrical connector at the back of it, take the connector off, mine had 2 phillips head screws holding the valve in place, once removed the valve slides out, and you can proceed to clean it. make sure you get all the black soot out of it and play around with it until it opens smooth, reinstall and it should run fine. to find out the exact location of your idle air control valve id google it or try a nissan forum, but itll be close to your intake manifold near the firewall. best of luck, once found its a very easy fix.

Try to clean the throttle plate with a tooth brush and B-12 chemtool (parts store will have). Engine off / remove air inlet duct, open throttle, spray a little and clean thoroughly.