I have a breaker that keeps blowing I traced the wire and unhooked it from the junction box everything else is working in junction box now but if I hook wire back in to it it will blow breaker again how do I find what is causing it to blow on this wire

everything else is working in junction box
What does that mean. If you remove the power in cable from a junction box everything left in the box should then be dead.

You have a short after the junction box. If you know the breaker hot is OK, disconnect all the wires in the j box and start connecting each pair to the hot lead. One of the sets will trip the breaker assuming there is more than 1 pair.