4.3 ruff idle

i just bought a 88' chevy blazer, i noticed that when its at low idle or when accelerating????? Anybody know an possible problems an solutions????

has it been tuned-up and servised?

What size engine do you have?

alright sorry i didn't give more info, My blazer has a 4.3 V6, currently have done no tune ups, but are finishing up on a new gas tank,sending unit,lines,rebuilding all back brake componets, an new back lines. i do not hear any knocking or anything just a vibration?

automatic,?

My blazer is an automatic, 4x4 an recently in the last year had an oil pump put in it. the motor looks great, an not any oil leaks, it's one of the cleanest i've seen for the year.