Hey everyone. I'm brand new to forum.

i really apologize if this is a repeat question but I'm in a bit of a rush to try and figure out what is going on with my Blazer.

I just bought and 86 s10 blazer. When I first start the truck it drives fine in 1st and 2nd gear but after driving for 5-10 minutes, even if I'm giving it steady gas the truck bucks until and will smooth out after a certain speed. Then when I shift to 2nd does the same thing. 3rd is generally smoother. Also, another issues is after driving for a short time when I open the gas cap a lot of, I'm just gonna say air, rushes out of the tank. At least a few seconds.

I'm really unfamiliar with manual transmission so I'm very sorry if some of my terminology doesn't make sense. Really appreciate any help or advice.

Thank you.