My car idles very high when stopped or first started and sometimes dies

I took my car to an auto part store to have it plugged in to see what was wrong with it. They said I needed a new control valve and a mass air flow sensor. I bought and had both of those changed. No other codes showed up besides those ones. My car doesn't idle as bad as it did before we changed these two parts but it is still idling very high when you are stopped or slow down. It sometimes dies. We also put a can of fuel injection cleaner in the gas tank. Nothing seems to be working with it idling so high and dying. It also gives off a funny smell when it idles sometimes. The smell doesnt happen everytime it idles but does sometimes. I need help with getting this fixed!