Help! My engines RPM goes down alot when I stop!

Hey wsup everyone, i'm new i just got the protege 2-3 months ago. My recent problems with the car is when I'm stopping at the light or stop sign, my rpm goes down below 500 and rises up to 750 after 2 seconds or so. It felt like it was going to die on me. Well today I checked the spark plugs and they're good. I have a hunch its the battery because when the car is parked and I roll down the windows, the rpm would decline as well. Can anyone help me out!!

i think that it has to do with the o2 sensor. the electrical system should bog down a little when you use electronics, especially in older cars. as long as it isn't killing the engine to roll down the windows, you should be alright. this sounds like either the IAC valve or the o2 sensor is fouling.