2012 mustang GT rough idle

What is your question?

I have a 2012 5.0 mustang with 70,000 miles. I am experiencing a rough idle fluctuating from 400 to 800 RPM and sometimes almost dying. It has no problems once on the road other than when I am stopped or sitting.

What makes this problem better or worse?

Nothing so far.

How long has your 2012 Ford Mustang had this problem?

a couple of days after purchase. I have had the batt. disconnected but it was doing it before that.