I have a 04 Aveo the original problem started about 6 months. nobody could find the problem.my friend bought the car new. when you drove the car it would lose power and stall very intermittently..the car would start right up and then run fine ,until the next time it stalled ,no time or pattern ,it varied .NO codes showing..he took it to 2 shops and the dealer. The list starts:complete tune up plugs wires, coil pack, throttle cleaning.etc they said they couldn't make it stall..so he read some forums and i helped him change the fuel pump and ran a couple cans of sea foam in the tank in case there was any water in the tank..didn't help ,then the catalytic convertor..no help ..he moved and i bought the car from him..so i cleaned the throttle body .installed a new EGR valve.motor still stalls,and NO CODES..next throttle postion sensor that did fix a very low idle..the car now not only stalls out it is running were bad with a intermittent missing. i was bound to figure this out .compression test cylinders were all even with in 1%or 2%..the motor broke the timing belt 16000 miles ago..so new head and belt..this year model did have a problem with failing valve springs that caused a miss.so that has been eliminated.so next the hose to the air box was torn so a replaced it with the cold air sensor and this helped the missing tremendously... the car did stall out more when it was hot .So finely i changed the computer..used.. this fixed the stall problem !!!Now check engine light is on.intermittent miss code..again new plugs ,wires ,valve cover gasket that was leaking,crank sensor,which fixed the missing. still have the code light .could it be the o2 sensor with no code? car runs great and gets 27 mpg around town.I used to be a professional mechanic, so with ego bruised please HELP!