I recently bought a older home. I am replacing my over the kitchen light fixture with a track type light. I am also remodeling my kitchen at same time. I unhooked all light fixtures and reinstalled the main kitchen overhead light. It Works!! Now with that said, we are installing a over the range microwave. So I have to run a new outlet box for the microwave. I have 2 wires coming into the kitchen that was the existing over sink light. I want to put a junction box in and run a new wire to the outlet for microwave. While I was doing this I am replacing my switch for over the sink light. So with the 2 wires coming into the kitchen for the sink light I am trying to hook everything up but when I do this I am getting consist power to the over sink light even with lightswitch off. I checked for shorts, and completely did away with the light switch wire from the switch to the light and it still doesn't shut it off. Any suggestions??

First off, the microwave should be on it's own circuit. Ok, now to the light issue. It isn't clear what you are dealing with. Please descibe how many wires of each color you have in each box.

So with the 2 wires coming into the kitchen for the sink light

Tell what that means. Does it mean two wires (black and white) or does it mean two cables each with a black and white wire. Does "in the kitchen for the sink light" mean the light fixture itself or does it mean the light switch box.

Agree you should run a separate circuit for microwave. But if this light is only other fixture on the circuit you can probably get by using this circuit.