Nginx proxy_pass ssl nodejs socketio error (no replies)

I am trying to track down what is going on but an not having any success. I am using nginx as a proxy for ssl in front of my nodejs app. The http api works fine. I have the websocket on a separate subdomain. I connects sometimes but I have a ton of these messages in the error_log:

upstream prematurely closed connection while reading response header from upstream

Here is my current config: https://gist.github.com/codedmart/7182a10da31fcaa5143c

Any help or ideas on what to look for would be great.

Thanks!