Hello all, new member here! I must say how nice it is to have such an active community for these cars!
So, right to the meat of her:
I'll start by saying that the car is stock with the exception of an invidia q300 catback and a lightweight flywheel. It's also still on stock map.
I bought the car in february of last year with 100k on it, it now sits at 126k.
It was in need of a clutch when purchased so I snagged a stage 2 kit with lightweight flywheel early last year. The car ran excellent until about 2k miles ago when on the way home from vacation with the wife it began to misfire at higher boost (8.5ish psi), and also picked up a slight stumble at idle. This concerned me as i know how finicky turbo engines can be and so the car was parked for the last 2 months, only being driven if absolutely necessary. As an aside, the car has received regular 3500k mile oil changes with rotella t6 that included oil and air fliters at the same time. The misfire is only ever p0303 and p0304. When it first appeared it was accompanied by a code for the bank 2 OCV, exhaust. 2 weeks ago I had time on the weekend and decided to replace the clutch, at the same time closely following qauzimotos misfire guide on nasioc. Ill put those findings further down.
Also worth noting: When i purchased the car I gave it a solid once over, replacing all drainable fluids as well as seafoaming the engine just after the intercooler.
In regards to quazis guide, here are my findings:
1. During clutch replacement plugs were also replaced with oem ngk iridiums gapped at .028. Old plugs appeared to be factory and were a bit burnt.
2. Also replaced fuel filter during clutch job, and have run one bottle of seafoam, and one BIG bottle of lucas fuel injector cleaner over 2 full tanks.
Have not cleaned fuel injectors but did swap driver to passenger sides.
3. I have not checked valve clearance but compression was solid with a low number of 155 on cylinder 2 and a high of 173 on cylinder 4.
4. MAF cleaned thoroughly from both sides with CRC maf cleaner.
5. While doing the clutch i chose to drop the trans rather than pulling the engine and as a result needed to separate the exhaust, but all nuts at the downpipe and the flange between the factory cat and the invidia catback had turned to dust. As a result I dropped the manifold from the head and removed the entire exhaust in one piece. Upon reassembly every component was inspected for dry rot or tears/holes, and I removed all lines from the front of the engine in order to do a couple of the other things on qauzis list. All gaskets/ o-rings were replaced with new oem.
6. Also during the clutch swap was the installation of an HKS circle earth kit, replacing all factory grounds/ground straps. During this replacement I found that the strap from the head to the underside of the passenger frame rail was broken. I had really hoped this was the culprit but alas, it was not.
7. Cam timing was checked per service manual during clutch job. Well within spec, sensor pick ups and reluctor wheels cleaned as well.
8. Pulled PCV after engine had warmed and was greeted by the faintest wisp of blow-by. Certainly not enough to cause this issue.
9. Car was seafoamed when purchased, I will do again if another member thinks it wise.
10. Car does have a lightweight flywheel however the condition doesn't seem worsened by it. It will on occasion smooth right out and hold factory idle, misfire free.
11. During clutch swap coil packs were swapped from drivers to passenger side, no codes on cyl. 1&2, codes persist on 3&4.
12. Teed into fuel return line (after rail®ulator) and found 37 psi at idle, 42 psi with vac line off of regulator. A quick blast with the guage under the wiper and part throttle through 1st and 2nd showed a max of 54 psi at 4ish psi boost.
13. Front and rear O2 sensors were replaced with new oem units during clutch swap. Thank god for torches lol
14. A visual inspection of the crank gear confirmed its in pristine shape. The timing belt itself looked almost new with zero visible cracking on either side and strong tension.
15. Not applicable as I only throw codes for cyls. 3&4.
A couple more notes: The faulty OCV was confirmed via FreeSSM and cam angle viewing. However, I do not own a Tactrix cable and my buddy with one is busy with work for the forseeable future. That being said, the OCV was replaced with an off brand amazon part, and the code has not returned since installation. I think this cheap part may be the culprit, if anyone else has input on this all advice is welcome. As you guys can see i've come at this thing 15 different ways and id rather not just start throwing parts at it. I own most tools necessary for troubleshooting/ general work so if theres something i may have missed checking let me know!
Also, the battery was reconnected while the ecu was disconnected from the BCM, in order to release the parking brake while removing the driveshaft. I believed this to be the cause of these numerous communication codes im also reading. Sometimes i can drive 45 miles without them coming on, other times they come on when i start the car in the morning for the first time. I've done a battery disconnect overnight and that made no differnce.
Here are all codes currently stored:
VDC Codes:
1- U0110 Lost comms with drive motor control module "a"
2- U0107 Lost comms with throttle actuator "a" control module
3- C10CA I understand this is related to the electronic p.brake recall for 5th gen legacys and outbacks?
4- C0057 ECM Communication Circuit
Im also getting code U1221 for the body control module, im not sure what this is other than a communications error?
And also a code 1A for drivers airbag failure. This has come and gone since purchased.
I've checked every fuse and relay with a multimeter and 12volt variable power supply to ensure relay function. I'm dead stumped on this thing, is there a chance these codes are related to my misfire issue? I must note that with exception of no cruise or tcs due to the misfire absolutely every other part of the car remains fully functional with or without codes. The misfires come sometimes one code sometimes both at once. When the other codes comes its always all 6 at once. Any help would be greatly appreciated, there are some really bright minds on here!
