So in my 13 for the past month or so I have had a rough idle/misfire like issue. The weird thing about it was that it didn't happen all the time. It stopped doing it for awhile until this past Saturday when the engine light came on for a P0300. I cleared the code since the dealer was closed and drove. I ran the tank down low thinking it may have been a bad mix of gas. I filled up yesterday and the car felt fine. Consisten WOT pulls and everything. Until today..I get out of class, start my car and it is idling crappy as hell. Then as I'm pulling out, the engine light comes on. I thought perfect. So I went to the Subie dealership and let them check it out for the second time for this issue.
Tech scanned it and the miss was jumping between all 4 cylinders!! Weird huh?
So he comes out and talks to me for a bit. He mentions that there is a ground wire that splits into 4 separate wires and there has been issues of the connection coming loose. I thought, well, an electrical issue would make sense since it doesn't do it all the time. He peeled back the wrapping and dropped some solder on the connection and what do you know...The miss is gone and it is smooth as hell.
Just wanted to share this with anyone who may have the same odd miss issue with their 08+ WRX or STi.