Help!! I have a 96 and when I hit passing gear it bucks back and has n power. It doesn't always do this, it seems like more so when it is cold. Any suggestions on what it could be?

i was going to vacation and i was bogging out. i thought it was only because of the long drive but i was only runnng on 3 cylinders because the spark plug was out. Get them replaced asap and it should fix the problem...