Recently, my automatic '86 Blazer would idle fine in park and neutral, but upon switching into a gear (R or D) would die. I got around this by giving it gas immediately when switching into gear and it would go and idle fine thereafter.

It still idles fine in park and neutral, but now it dies several times in gear before it will get going, and once it does get going idles horribly. Almost to the point that if I dont switch into neutral when stopped it will die on me. (does this both cold and fully warmed up)

My guess is a bad choke (In which case a new carburetor)... but could a simple tune-up fix this?

Thanks!

 

If you have a Quadrajet carburater, chances are you have a weak or poorly adjusted choke pull off (vacuum brake) on the side of the carb.. If it's weak, it may be allowing the choke to close when you put it in gear.
Worst case possible is a carb overhaul, which is a lot cheaper than replacing the carb.
I overhauled my carb a couple of months ago, it was full of crap. https://blazerforum.com/m_38627/tm.htm