Possible short in circuit misfires and smokes when I put in twenty watt fuse

I have had problems with it lately and its driving me insane! I had a twenty watt fuse in it that controlled my cars computer, analog clock, horn, courtesy lights, floor lights etc. I was have problem while the fuse was in so I unplugged fuse. Car ran great. I put fuse back in and problem starts again! Misfires and smokes! When I take fuse back out runs fine again please help me!