I actually made this post on a few other forums almost a month ago on 9-10-2013. Forgot about posting it on here as well.

 

It is in this section of harness

 

Wow, how many times in life is an engine fix really that simple?! Great info man, thanks for passing that along. (And glad it's back to normal.)

 

Great that they found it quickly as little electrical gremlins like this can take awhile to diagnose and fix.

 

I've been having a similar issue for quite a while now. Saw this thread and I decided I would take a look(didn't want to involve the dealer because of mods).

This seems to be the ground that branches off into 4 other wires.

I dropped a big glob of solder on it.

Took the car for a drive and it didn't misfire, but it doesn't always so time will tell. Thanks for this thread either way.

 

No problem man. Thanks for the detailed pictures so everyone has a better idea!

 

it actually seems to have worked..so far anyway

 

so update on the issue? has it completely fixed your misfire? i have a '13 wrx as well. car is protuned and everything else is fine, except for that annoying rough idle and only the p0300 cel popping up. ive narrowed it down to it being the wiring harness issue. i cut open the tape and im digging through it. im assuming its the one cable thats wrapped in tape like crazy?

 

You follow those exposed silver ground wires to the end where they are all joined together by that little clip which is wrapped in tape if I remember correctly. The problem totally went away in my car.

 

my wiring harness doesnt show any exposed ground wires. unless if theyre covered by the electrical tape?

 

yeah sorry I forgot about that layer of tape

 

wow. so i added the solder. it idles like a dream now. usually ill get 1 or 2 idle roughness counts on the accessport (most i got was 5). but when driving around town, idling in between stops, i didnt even get 1 idle roughness count. accessport just read 0 the whole time. im really happy now. Thanks slushy and 99pgpgt. you guys solved 3 months worth of headache for me. i always thought of the worst as ringland. now i can sleep well tonight.

 

yeah I was dumbfounded when this actually worked

this should be a sticky

now my new 2015 has little misfires at idle lol, but I heard that is a DI thing

 

lol. nice. well you never know. it can always be that stupid ground wire issue.

 

Has this fix been holding on strong for you all? I have a 13 WRX with a few mods so I didn't want to take my car to the dealer. Car has always ran flawlessly until about 2 weeks ago I got P0300. Cleared that code and it ran fine for a about 2 weeks. Now check engine light again and this time I ran the code with my accessport rather than generic code scanner and it shows PFFFE which seems to mean roughly the same thing. I just did this solder fix and cleared the code again. Hopefully this solves it.

 

The wires are inside a harness and float. They're suspended in the air, kind of acting like their own little shock absorbers in a way. They're soldered and crimped. There's no way vibration loosens any connections on this joint. I can't see that happening. Someone had to have been messing around in there for something to happen. Mine had this black tar all over the connection, and noone ever mentioned any tar in the previous posts. That makes me think someone was in there. For what though I have no idea.

 

Wrong black wire



I did the same thing. You unraveled the wrong wire. the one you unraveled started as one and separated Into 4 at the bottom. The one you need to unravel is a smaller black wire that starts as 1 and goes into 4 at the top. But you can't see the 4 wires it separates until you unravel it. Once you unravel the right one there will be no black tar like you described. It's silver meshing just like the above picture. I think the one you are talking about is copper wire, anyway. Hope this helps and you see it!

 

Any updates?

 

I just did this today ... Car seems to idle better. Only time will tell though because it was an intermittent issue. Thanks going out to the OP for this!

 

Let me just say, I have not kept up on this particular thread as I am not on here as much as I am on nasioc. Another nasioc member linked back to this thread on my post on that forum for this issue. I have to say that I am impressed with the help given on this subject so far. As for one thing, the main harness plug is solidly mounted on the bracket to the strut tower, I have no doubt that with any chassis flex, engine vibration, chassis vibration, that it pulled loose from the connection. IMO, subaru could have done a lot cleaner job of grounding the coils.

 

I know this is an old thread but my 2013 wrx just go this p0300 code and i searched online for an answer to why it happened and came across this thread. Also i have noticed with my car before the CEL lights came on that it would have a really rough idle at very unfrequent times. I just did this solder fix yesterday and i will update in a week or so to let you guys know if my rough idle had went away or not. Just for a day it is fine but like someone else said only time will tell. I hope this works cause i would hate to take the car to a stealership.

 

As a lurker I found this thread that seemed to fit my issues with my 2013 WRX Hatch. I followed along and found the same wiring as shown in the pictures. I didn't have a soldering iron so I cut the connection out and replaced it with an uninsulated style connector. I used the appropriate crimping tool, one with a "tit" to actually make the crimp and not just a squish(that would come loose again). Been working fine since.

Thanks for the knowledge. I spread it to the local dealership here, who has been trying to figure it out. He is a good tech and worthy of such a heads up.

 

I have same issue w/ my 2016. Will be looking at making the fix this weekend... Crazy that SOA hasn't picked this up and offered the fix?

 

I have been having the same symptoms with my 2011 WRX for a long time now (a couple years) but it has been very sporadic. Recently, however, it's been getting worse and today I thought it was actually going to die (very rough idle). I found this post, which was the first to describe my exact symptoms (randomly occurring misfire on all 4 cylinders, checked all the usual stuff that commonly causes misfires and nothing seemed to help), followed the instructions, and it idled and drove perfectly on the test drive! I'm hoping it was as simple as this, and I hope others who have this seemingly common mystery issue find this post like I did. Thanks!

 

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. Consistent 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.

I know it may not apply to me but, I have a 2008 legacy GT that is having can buss issues with code P0600. I think its a ground issue but not 100% sure. do you think this might cause an issue outside of misfire? When my issue happens I have rough start up idle for a few seconds then its smooth but as I'm driving my temp gauge pegs out, check engine light starts flashing as well as cruise light and car goes into reduced power.