when is getting warm outside the engine is running intermittent

[thekraki]

Help!!!!!!!!!
I bought a Geo Prism Lsi 93,and when its getting warm outside (over 50),the engine is starting to act funny,its working intermmitent,and will run if i press a full gas to it....and this goes on an on.When the outside temperature is below 50 it runs good.....but the simptoms are the same if the engine warms up too.And when the engine is fooling arround the check engine pops up,but as soon as i press a full gas and the engine is reving up the check engine goes away.....help please.....i cant afford another car right now