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12-10-2012, 09:48 PM | #1 |
Scooby Newbie
Member#: 269203
Join Date: Jan 2011
Chapter/Region:
TXIC
Location: The Woodlands, Texas
Vehicle:2005 WRX STi WRB |
Help me diagnose this
This will be a slightly long post, but I need some help on this:
Here is a little info on the car: 2005 STi stock ECU with dyno tune built motor - rebuilt stock heads JE forged pistons BC rods + bolts ARP bolts/studs galore bored to 100mm cosworth head gasket had a compression test at around 15k before I put on the rotated kit and everything was good. motor has 19k on it with the following main mods: GTX3076r rotated kit @ 24psi Aquamist 100% alky injection perrin EL headers, up pipe and down pipe Tial 44mm EWG with dump tube Tial Q BOV TGV deletes ID 1000cc injectors perrin fuel rails Aeromotive FPR Walbro 255 FP Grimmspeed AOS Stock flywheel ACT 6 puck clutch No lightweight pulllies on the motor Dyno Tune by a very good tuner - 410WHP 400WTQ - Dyno dynamics Here is my issue that I can't figure out: So after I got my car re-tuned for colder weather (just a tune up more or less, not to gain more power) I drove the car back home and filled up with 93oct shell like always. The next day, I was pulling out of my driveway and the check engine light comes on. I get it checked and its a cyl 3 and 4 misfire. I also notice the idle to be rough (surging), but under normal crusing and all forms of acceleration, no issues. I decide to change my plugs with NGK 1 step colders (was using Denso 1 step colders) and gap them to 24 thou, which is what the tuner recommends - I swaped the coil packs too (cyl 1-3 and cyl 2-4). I reset the ECU and drove the car around normally. I Noticed the idle to still give me issues, but no CEL. After 120 miles of driving, the CEL came on again with cyl. 3 and 4 misfire. If I remember correctly, at this point I refueled my car with shell 93oct and then put in a can of sea foam. - no improvement. I then burned out about 75% of that tank and filled it back up with shell 93oct again and still no improvment. - I think i've ruled out bad gas.. I then start to take logs at this point. I notice that when Im at idle and first start from a stop, I get periodic misfires on all cylinders, but mainly 3 and 4. However, 4 seems to have a bit more though. When I come to a stop, the idle is perfectly normal for about 15 seconds and then starts to slightly surge and you get the occasional misfire. I then decided to send my injectors into my tuner to get flow tested and cleaned. Cyl. 2 and 4 injectors were slightly lower than the other 2 injectors, but were still good. Anyways, the cleaning got them all back to flowing the same. I put the injectors back in (all same cylinders) and i still have the same issue with the CEL. The idle seems to be slighty better (still surges), but the tuner did send me a map to raise the idle to 1000rpm too. I have taken logs and sent them to the tuner - AFRs normal, no knock at all, no misfires under normal driving or full power, no white smoke under boost etc. At idle though, my wideband (and stock front 02) seem to jump around a little much (due to surging though..). I should also add that when im crusing and im holding a constant speed at low RPMs (1-2.5k) the car feels not so smooth and you can feel it miss sometimes. However, anything beyond the lower RPM range is just fine and the car runs with out issues. I just ordered a new fuel pump and install kit so I could also get another filter, but if this does not fix it, maybe the front 02? I don't think it could be a damaged motor? I would see signs of lots of blow-by, loss of power, starting issues, etc.. I dont have any of those though. What else could this be? |
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