First off, thanks to all who contributed here. I had this EXACT issue on my 2012 Eco (49k miles). Check engine light came on, surging idle etc. I went to the local autozone/oreilly and had code P0171. I started searching through the forum and thankfully came on this thread. Knowing virtually jack diddley about cars I checked youtube and how to sites. All boiled down to the PCV valve failure like most other posts here. I have extended warranty and the replacement by the dealer was covered. I guess next time I’ll have to do it myself.