Why does my 1999 Pontiac Sunfire stall ONLY during warm months?

during spring/summer when gets 60 degrees or over, stalls , have hold key down 10 seconds before starts. when start first time day, anytime after that, starts normal until it's sat overnight or long period of time. but, when it's cold in fall/winter, starts no problem. has been way since july of '02 when bought car 37,000 miles on it, , took dealership purchased week after got fix it. said starter , put new 1 on, still , has. got remote starter put on in '03, , in summer won't start @ if try use remote...it tries 3 times, gives up. remote start works great in colder months, though, know there's nothing wrong it. possibly be?

during spring/summer when gets 60 degrees or over, stalls , have hold key down 10 seconds before starts. when start first time day, anytime after that, starts normal until it's sat overnight or long period...

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