1. Add more of what your character is thinking.
Even in an action scene it's okay to take a breath and understand what's going through your character's mind. Readers want to know these things.
2. Add action beats in between dialogue.
What is your character doing while he/she is talking? Show us.
3. Take time to describe the scene.
I'm not talking purple prose here, but a few lines of description can go a long way.
4. Read this article called "Stretching the Tension" by James Scott Bell.
It's invaluable. The info can also be found in his book Plot and Structure.
Now if your problem is that your scene is moving too slowly, do these steps in reverse. TAKE OUT some of these elements.