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Old 02-03-2015, 01:49 PM   #1
steeez
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Default 06 sti Problem! Need advice/help

Hey guys having trouble with my subie, it starting stumbling really hard like almost jerking the whole car lunging forward in boost (like your learning how to drive manual in 1st gear all over again) it back fires as it's doing it and I had a code which was basically the o2 sensor but it came up once and I cleared it and never came on again. The problem is really easily duplicated by WOT in 1st, 2nd, 3rd gear 4th 5th 6th are totally fine which I find strange. I've come from the honda scene and have a faulty o2 won't cause this so this is all new to me. Can anyone help with the situation before I buy an o2 and cross my fingers lol

Car: 2006 subaru STi
Engine mods: stage 2 from Cobb AP

- invidia catless DP
- invidia race catback
- k&n short ram intake
- tomei UEL header & up-pipe

Nothing special but I thought I'd give you guys the mod list just to clarify I didn't change much.
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Old 02-03-2015, 02:51 PM   #2
mrjason
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Go back to the stock tune an see if it is still causing issues.

Check your intake for leaks / intercooler Y pipe for leaks.
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Old 02-03-2015, 02:53 PM   #3
Zefy
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So WOT is totally fine? But everything else is terrible?

What was the o2 sensor code? Front or rear?
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Old 02-03-2015, 02:57 PM   #4
steeez
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Quote:
Originally Posted by mrjason View Post
Go back to the stock tune an see if it is still causing issues.

Check your intake for leaks / intercooler Y pipe for leaks.
Definitely trying that when I get home. Will it not affect anything if I run stock tune with all my bolt ons?
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Old 02-03-2015, 02:59 PM   #5
steeez
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Quote:
Originally Posted by Zefy View Post
So WOT is totally fine? But everything else is terrible?

What was the o2 sensor code? Front or rear?
WOT 1st 2nd 3rd in boost is when ur jerks and bogs. 4/5/6 I can boost WOT no problem.

Sensor code was front o2
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Old 02-03-2015, 03:42 PM   #6
Mad_Max_2010
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A bad o2 in my car made it basically undriveable. Could it be bad gas?
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Old 02-03-2015, 04:07 PM   #7
yoall
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Check your spark plugs.

Mine was jerking at WOT. changed them out and never happened again.

Good luck.
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Old 02-03-2015, 04:53 PM   #8
Zefy
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Quote:
Originally Posted by steeez View Post
WOT 1st 2nd 3rd in boost is when ur jerks and bogs. 4/5/6 I can boost WOT no problem.

Sensor code was front o2
Sounds like it might be the o2 sensor. Closed loop control is buggy (o2 sensor controlled) while open loop is fine.

I would say take some datalogs and see what the sensor is doing.

Plugs could also cause problems like yoall said but it typically gets worse with heat so why it would work at higher gears/load...?
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Old 02-03-2015, 08:30 PM   #9
steeez
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Quote:
Originally Posted by Mad_Max_2010 View Post
A bad o2 in my car made it basically undriveable. Could it be bad gas?
Could be, I've used 91 shell with no problems before hmm
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Old 02-03-2015, 08:32 PM   #10
steeez
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Quote:
Originally Posted by yoall View Post
Check your spark plugs.

Mine was jerking at WOT. changed them out and never happened again.

Good luck.
Did it happen in every gear? I'm thinking it's o2 maybe kus the o2 can properly read 4/5/6 gear AFRs properly but not 1/2/3
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Old 02-03-2015, 08:39 PM   #11
yoall
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iirc, it was all gears. Even when I was cruising. The engine would feel like it was bogging when I steeped on it.

Make sure the spark plug are gapped..

My km on the plugs were due. So I just switched it out.

Sent from my SGH-T889 using NASIOC mobile app
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Old 02-03-2015, 10:41 PM   #12
steeez
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Quote:
Originally Posted by yoall View Post
iirc, it was all gears. Even when I was cruising. The engine would feel like it was bogging when I steeped on it.

Make sure the spark plug are gapped..

My km on the plugs were due. So I just switched it out.

Sent from my SGH-T889 using NASIOC mobile app
Mine is only in boost/WOT. I can drive my car perfectly if I stay out of boost.
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Old 02-03-2015, 10:51 PM   #13
yoall
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Sorry. I meant when on Highway cruising. I wanted to wot. It would bog. I can drive it fine. Only when I stepped on it. It wouldn't pick up. No cel either.

Sent from my SGH-T889 using NASIOC mobile app
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Old 02-03-2015, 10:53 PM   #14
steeez
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Quote:
Originally Posted by yoall View Post
Sorry. I meant when on Highway cruising. I wanted to wot. It would bog. I can drive it fine. Only when I stepped on it. It wouldn't pick up. No cel either.

Sent from my SGH-T889 using NASIOC mobile app
Would it full on stutter and basically limp?
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Old 02-03-2015, 10:56 PM   #15
yoall
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Stutter in the low rpm (3000) until it picked up speed. You can say, under load. It would bog.

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Old 02-04-2015, 01:38 AM   #16
SStiNA
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Maybe the MAF sensor? your problem sounds exactly like my old cobalt's problem that ended up being the MAF, maybe just try giving it a clean.
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Old 02-04-2015, 12:41 PM   #17
steeez
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**update**

So I checked my couplers and so far all are tight, right before it's bogging like **** into boost it hits around 15 on the AP AFR readings. I always thought it hits 11 or 12 and it's probably leaning out so it dumping more fuel and that's what causes the loud backfiring correct me if I'm wrong?
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Old 02-04-2015, 01:25 PM   #18
2010 WRX Limited
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+1 for sounding like MAF sensor or something in that area. Incorrect MAF scaling, changes to the intake or faulty MAF will make the AFRs go wacky in open loop and causes stuttering and backfiring. In closed loop the o2 sensor can allow the ECU to compensate for the buggy MAF so that may be why you're only getting it in open loop (WOT full boost)

Suggestoion: Bribe someone with beer and pizza to come over with his car and swap in his known working sensors one at a time to troubleshoot.
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Old 02-04-2015, 01:30 PM   #19
Zefy
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mafs usually don't just stop working when the car gets into boost. That's not how they operate. (unless you're running a blow through maf... which by the sounds of your mods, you're not...)

So you had a front o2 sensor code and your car was pulling fine up until it started reading weird... a datalog would really be better for this though...
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Old 02-04-2015, 05:16 PM   #20
2010 WRX Limited
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Quote:
Originally Posted by Zefy View Post
mafs usually don't just stop working when the car gets into boost. That's not how they operate. (unless you're running a blow through maf... which by the sounds of your mods, you're not...)

So you had a front o2 sensor code and your car was pulling fine up until it started reading weird... a datalog would really be better for this though...
Stop talking such logic! just kidding... that's a good call. A datalog is the way to go.
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Old 02-05-2015, 09:02 PM   #21
steeez
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I'll try to data log it, at this point I'm trying to get the o2 code to come up nothing still. Imma try with smoke testing for boost leaks. spark plugs after as it only hesitates like crazy in WOT. Then if all fails o2
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Old 02-06-2015, 12:14 PM   #22
slowguy
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Have you considered wider wheels?

..................
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Old 02-06-2015, 12:14 PM   #23
slowguy
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:d :d
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Old 02-15-2015, 03:19 PM   #24
steeez
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Changed and gapped the plugs same problem, now it jerks like crazy in all gears in boost now. I've checked physically for boost leaks nothing I can see. I got the o2 code back but could it really be my issue? Running out of ideas here and ready to call the subie a day. Haha
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Old 02-15-2015, 04:45 PM   #25
FunkMasta
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what is the exact code, and do you have freeze frame data?
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