Check Engine Light/Rough Start

I have a 91 S-10 Blazer 4.3 throttle body injection.The "Service Engine Soon" light comes on when the temp outside drops below freezing, and I have to turn it over 3 to 5 times to get to start. I've checked fuel pressure, fuel pump for the starting, and only O2 sensor for the light.

are you saying you read the code and it turned out to be o2 senser? if so change it out and reset computer by unhooking the battery for awhile. then let us know how it goes.
o2 senser will cause a hard to start problem and rough idle.

get the codes read. It could really be anything

yeah, if you havent read them, you really do need to. autozone does this for free.

autozone said they can't read the codes on a 91. only on 94 & up. but i got my mechanic to hook his scanner up to it. he told me it was the O2 sensor. the problem now is, we can't get the old one out. he put a torch to it but was concerned about too much heat and damaging the cross-over. so i guess i'm stuck.