i have this 1990 lumina and it runs just great in cooler weather, but let it get above 80 degrees outside and the check engine soon light comes on and it stalls everytime i take my foot off the pedal... i have no clue how to fix it other then move some place where it stays cooler outside year round?

Which engine?

It would seem that the idle mixture is too lean to have a stable idle at higher ambient temps, so I'd be leaning towards at intake air temp sensor (not sure if that year had that, though), MAP sensor, or possibly the vacuum hose going to the MAP.

A sticking EGR valve can cause that, but I don't see where it would coincide with outside temp.

Which engine?

It would seem that the idle mixture is too lean to have a stable idle at higher ambient temps, so I'd be leaning towards at intake air temp sensor (not sure if that year had that, though), MAP sensor, or possibly the vacuum hose going to the MAP.

A sticking EGR valve can cause that, but I don't see where it would coincide with outside temp.

my car has the 3.1 V-6, i'll take a look at the vacum hose on that map sensor, if i can locate it... not really sure what i'm looking for though, i'm guessing it would be located on or near the air intake? it's really odd it only does it when it gets above 80 degrees and the weather has been warmer this past week, so the stalling is driving me crazy... thanks for taking the time out to try and help me...

My 90 lumina does have intake air temp. sensor. P :2cents: lugs in near front before air filter.Hard to check the map sensor vacuum hoses way back behind engine.The hard plastic hoses suck.

you said the check engine light comes on, do a code check by taking a paper clip and hooking it all up the link is http://jeffex.info/GMcodes.htm there are other links though, thats just mine, now it blinks each code 3 times, first a 12 which is normal, then another code. which is the problem code.