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Discussion Starter · #1 · (Edited)
Wassup!! 2017 Ford Focus RS with 35k miles

Been doing a lot of research in here about a idle issue I鈥檝e been having for around a week now. During driving conditions the car is fine, pulls fine and no hiccups but coming to a stop the idle drops and sometimes it鈥檒l drop enough to die. At first I only had the p2067 code so I had my primary o2 sensor replaced and I changed the spark plugs just incase. Ended up fixing that code, but the rough idle was still there. Now I鈥檓 throwing a p0171 so I鈥檝e read that the next step is the fuel pressure sensor, so I just replaced that today. Still has the same issue! (Might run a little better but idle is still rough).

Below are my mods
-CPE exhale kits( w/ tial BOV)
-ETS FOCUS RS INTERCOOLER KIT 5" blue
piping
-COBB motor mounts
-Turbo Smart Turbo Actuator
-COBB RS ACCESSPORT V3
-JSTuned
-Scorpion DOWNPIPE
-Borla Catback Exhaust System
-Mountune RS Full-Flow Intake
-ACT Perf Street Sprung - STG2 kit

kinda stuck on where to go next, I鈥檝e reuploaded the stock tune on the car then switched to Cobb stage 2+ And still no fix. Even tried stage 1 and so on. Currently just kept it on stage 2+ since I have the supporting mods for it. I鈥檝e been checking the AFR鈥檚 and while driving I鈥檓 around 14-15, under acceleration it goes as low as 12-13. My LTFT was all over the place prior to me replacing those parts, now it鈥檚 around -10 to 14 depending on driving. Sometimes at 0 and sometimes it shoots up to 45-50. I can get better readings next time I鈥檓 driving (I鈥檒l actually pay attention to the numbers, these are just me glancing at them) I鈥檓 about to check for exhaust leaks but I鈥檓 still stumped and would like to know if anyone else has had this problem. I鈥檒l attach pictures of the spark plugs when I changed them out

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this is after pulling into garage. Idle is ok, but from releasing clutch to move forward and applying pressure back, AFR jumps from 14 to 20. While driving, AFR is usually at 14.
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Discussion Starter · #11 ·
Aye guys have a update, ended up being the injectors. Just replaced them and so far so good. Will update if any codes come back but idle is good! 馃馃徏
Also reverted back to stock tune until I can get a legit one
 

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Discussion Starter · #17 ·
So now my code is back, but idle is good (maybe not perfect but definitely better) and it doesn鈥檛 die anymore. Unplugged battery and everything, still shows. The troubleshooting continues, at least for that damn code
 

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Discussion Starter · #18 ·
Your first list says JST tuned?
Why not stick with Brian, can't go wrong with his work IMO
When I bought the car, it was suppose to be tuned by them. When going to view current tune on my COBB, it would always freeze and nothing would show. So when I started having all these problems, I reset the COBB tuner to restore all tunes and then uploaded the Cobb stage 2, now I鈥檓 running the stage 0 (which I鈥檓 guessing is stock tune). But like stated above, I guess these off the shelf tunes or stock tune doesn鈥檛 register the turbo smart WG. So now I鈥檓 trying to figure out what to do next 馃し鈥嶁檪锔
 

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Discussion Starter · #20 ·
Does it idle rough right when starting it, or does it do it after a while? If it's rough right away, what's your STFT doing? I had a similar issue a while ago, and threw the parts cannon at it (new injectors and coil packs even). It ended up that the upstream o2 sensor I put in (to try to address my miss fires at idle) was faulty, and replacing it again fixed my issue. That probably is not your issue.

First see if you can get your intake smoke tested. A leaky intake shouldn't cause your issues unless it's happening between your intercooler exit and the head, because of the MAP sensor locations. But it's still helpful.

Another test I found useful was that my car would run fine after I reset the ECU learning. After running for about 15-30 seconds, it would start learning again and idled bad. If yours does the same, then you should be able to narrow it down to be related to one of the sensors.

edit... I'll add that it could also be something that is affecting the sensors. The only thing I'm thinking of is if your downpipe doesn't have a good seal to the turbo, it can scavenge outside air in, so your o2 thinks it's running lean, and will continue adding fuel. <-- That's what my guess would be the issue... if it runs fine after clearing the KAM.
I鈥檓 going after exhaust leaks next. Then the tune since I鈥檝e already replaced the o2 (hoping it wasn鈥檛 defective)
 

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Discussion Starter · #21 ·
More updates!
went with a custom tune from Alan Jackson, on revision 1 right now but stopped the process because even that did not fix my idle issue. Gapped my plugs, replaced upstream o2 sensor again (just incase my previous was faulty) and still having rough idle. Went back to stock OEM tune for ****s and giggles and my rough idle went away? But I still have p0171 popping up and now a p219A. Havnt been going into boost, but when I do I notice a lot of black smoke out of exhaust. Pics of my o2 sensor will be attached. Going with fuel filter next and when I get my car shipped to New Jersey, I will finally be able to get it smoke tested and maybe walnut blast the valves if no leaks are found. Will also be doing a compression test soon
 

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Discussion Starter · #22 ·
Another update!

Changed fuel filter, no change. It was easy to do though and I read that it鈥檚 recommended every 30-50k miles. At this point I鈥檓 trying to be positive and say I鈥檓 doing 鈥渞outine maintenance鈥 馃槀

I did complete the compression test, and numbers are as follows
178 cyl 1
178 cyl 2
178 cyl 3
180 cyl 4

So thank god that came out good. Still having rough idle on custom tune but good idle on stock tune (still shows codes though). Will do more troubleshooting after car arrives in Jersey at the end of June or start of July 馃馃徏

Edit:
Also found out that my head gasket recall was done at 3k miles. Currently at 37k
 
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