Going from first to second it won't shift into second unless I let off the gas. If I stay on it it will stay in first. All other gears shift normal.

 

Verify that the TPS (throttle position sensor) is within spec and the sweep is clean and linear.

Speed sensor can throw it if too, does your speedo work correctly? If not, the speed sensor in the Trans might be shot.

 

What do you mean by the sweep?