hi...new to the site ...but i have been searching for an answer for my 2004 automatic aveo....couple of years ago it started stalling ...but this happens only when it is warm....and only after i have turned it off for a few minutes...like going shopping....when i return ....car starts right up ...but when i accelerate it will not shift into the next gear and will die.....the only way i can save it from doing this is by shifting into neutral and revving the engine.....once it does get going it will not show these symptoms unless i turn it off and wait a few minutes......so again....never stalls when starting cold..only after it is warm....will start and idle fine...but if i accelerate it will go to about 25-30 k rpm and then lose power....only way to stop it from stalling is to shift into neutral and rev it pass those rpms....then it is fantastic for rest of the drive....never dies at lights etc
problem is worse in the summer than in the winter

other facts
gets between 22-28 mpg depending on season..i was hoping for better when i bought it
ive changed spark plugs
cleaned throttle body

ive tried to clean the iac valve but couldnt get it off

replaced air filter
no codes ..no check engine lights


any ideas from the pros out there?....im not very car savvy....thanks for any futre help w/ this drew