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Old 01-16-2013, 04:24 PM   #1
Thunderbird28
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Default Bucking/ Power Loss and Running Rich

How it going everyone. Ive got an 07 wrx with a TXS turboback exhaust and stage 2 tune. In the last couple of months my car has had a bucking/stumble/power loss or whatever you want to call it that happens between 2-3k rpm. It does this on flat ground but is worse when Im driving through the canyon. The last couple of times it stumbled and bucked pretty bad and eventually put the car into what seemed like limp mode. I was only able to get 5 psi of boost and what not. However, I haven't gotten a single CEL from any of this. I have also noticed that my car seems to target 13.7 afr and not 14.7 (verified with WB02).

All this happens during cruise and partial throttle... if i floor, the car runs great, and afr are where they should be. These problems have slowly gotten worse and I would like to take care of whatever is causing these issues. Has anyone ever had a problem like this or ideas on what to check or test?
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Old 01-16-2013, 04:57 PM   #2
nmlittlebigman
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Maybe front O2 sensor going bad if you are seeing 13.7 on wideband in CL fueling. Or possibly vacuum leak. Just a guess.

Last edited by nmlittlebigman; 01-16-2013 at 05:07 PM.
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Old 01-16-2013, 06:15 PM   #3
tomkun
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Try cleaning the maf sensor.
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Old 01-16-2013, 07:04 PM   #4
niemkij
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The above check for sure. Dirty air filter possibly?
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Old 01-16-2013, 08:35 PM   #5
Thunderbird28
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Alright, Ill definitely give it a clean. Also is a there a way to test the O2 sensors without having to drop $250 on new ones?
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Old 01-16-2013, 09:35 PM   #6
nmlittlebigman
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Start with the easy stuff like cleaning the maf as tomkun says. Then check for leaks . You may be losing air after it was metered by the maf which would explain why you are too rich. It would be nice if someone nearby with a tactrix cable could pull a learning view to see what your AF learning looks like.
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Old 01-16-2013, 10:13 PM   #7
Thunderbird28
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Definitely would like to do the cheaper/easy stuff first. Agreed on the tactrix. Unfortunately mine broke about 2 months ago, but my AF Learning always looked good in the past.
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Old 01-16-2013, 10:39 PM   #8
nmlittlebigman
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Quote:
Originally Posted by Thunderbird28 View Post
Definitely would like to do the cheaper/easy stuff first. Agreed on the tactrix. Unfortunately mine broke about 2 months ago, but my AF Learning always looked good in the past.
Well in the past your car ran fine too..so its definitely worth a peak . If we could get a learning view and see the AF learning in A,B,C,D we might be able to nail down if its a vacuum leak or a boost leak somewhere else in the intake track. We could also see if and where you are getting any FLKC knock. Otherwise skipped to plan B and build a leak tester and make sure everything is buttoned down:

http://forums.nasioc.com/forums/show...st+leak+tester

If you clean your maf and leak test your car first then you could narrow things down. The only reason I suspected O2 sensor is that car runs fine in boost (Open Loop fueling) because at that point your ecu ignores the front o2 sensor altogether and fueling is done strictly by the tables.

good luck
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Old 01-17-2013, 08:00 AM   #9
jaxscuby
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tuned? or off the shelf map?

your closed loop fuel needs to be adjusted.
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Old 01-17-2013, 12:29 PM   #10
Thunderbird28
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Its opensource tuned. I used a stage 2 base map and then fine tuned it. Like is said, the tune ran fine for about 1.5 years. I reset the ecu yesterday to try and determine if it was a tuning issue but even on the freshly reset ecu, it still had its issues which leads me to think its mechanical... Im leaning towards a leak or bad 02 sensors.
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Old 01-17-2013, 01:34 PM   #11
mechatricity
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Just a tip, i know my 06 (and i believe the 07) can still use the 1.3U tactrix cable, which you can no longer buy from them, but can buy from evoscan.
http://www.evoscan.com/evoscan-gps-o...flashing-cable
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Old 01-18-2013, 01:03 AM   #12
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I would check for boost leaks, exhaust leaks, and then O2 sensor. Getting a log of the car would help point you in the right direction faster.
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Old 01-18-2013, 02:52 AM   #13
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As others said, first, check for leaks. Then, when time comes to check the O2 sensors, start with the cheaper narrowband sensor first.
If, for some reasons, the ECU does not obtain a proper response from the narrowband sensor (if it's dead or disconnected for instance), the ECU will change the closed loop target AFR from 14.7 to 13.5.
I learned about this not so long ago from Uncle Scotty. I always assumed the ECU didn't care about the secondary narrowband O2. But, I was wrong.
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Old 01-18-2013, 05:41 AM   #14
tac79phoenix
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Might even be a potential wastegate issue. Maybe need to get it checked out/adjusted.
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Old 02-28-2013, 12:26 AM   #15
amladineo
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ever figure what it was?. I have a very similar issue with my 07
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Old 02-28-2013, 02:36 PM   #16
Thunderbird28
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I haven't figured it out yet, but I haven't really looked at, cleaned, or changed anything. It actually hasn't had the problem for a while now so I decided not to worry about for now. Sorry aNd hopefully you can figure out what's wrong with yours.
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Old 03-01-2013, 11:21 PM   #17
dstroy
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See if you have excessive oil in your intercooler, and any in the hotside of your turbo. If so, bad shaft seals, 2-3k is when it starts really spinning up and that would explain the hesitation.
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Old 03-05-2013, 02:18 AM   #18
subaru_sti_steve
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From what youre describing it seems I wou, d check the fuel system. Check your fuel pressure and go from there.
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Old 03-05-2013, 12:02 PM   #19
Tripintaz
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Quote:
Originally Posted by Thunderbird28 View Post
I haven't figured it out yet, but I haven't really looked at, cleaned, or changed anything. It actually hasn't had the problem for a while now so I decided not to worry about for now. Sorry aNd hopefully you can figure out what's wrong with yours.
Maybe you had some bad gas
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Old 03-06-2013, 02:16 PM   #20
amladineo
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I have had the same intermittent problem for while a now. I have cleaned the Maf sensor checked all my boost lines and changed air filter. I took it to my mechanic and he said he found a issue with the fuel pressure reg, but maybe 2 weeks after he fixed it it started to act up again. I have been reading a lot about bad boost control solenoids and I share a lot of the same symptoms but don't know it those can be intermittent? It is very frustrating because the 2 times I have taken it to the shop it is not having the issue.
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Old 03-07-2013, 01:27 AM   #21
section8suby
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Well this seems to be an occurring problem with 07 's... I've got a 07 wrx with 64k miles and have had a very similar problem off and on for the last two years (started around 30k). Several trips into the dealer when under warranty they couldn't find anything wrong (no check engine light ever). Since warranty expired back in june I have changed exhaust (catless), intake ( back to stock), intercooler (sti), fuel pump (new filter cartridge), ebc (cobb), sparkplugs, cleaned maf (several times), intercooler hoses, and had a pro tune. After all that, problem came back after a couple months.
My tuner took a look at it last week but by the time I could get it there the car was beginning to clean up again. He found that the knock sensor was too tight ( was picking up odd knock situations ) so he re-torqued it and re-set the ecu. No more knock problems but the car lightly hesitated this morning which is a sign of the problem returning... I will continue the search for the answer and if I find the gremlin issue I will post it.
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Old 03-07-2013, 02:47 AM   #22
amladineo
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I too suspected a knock issue and when I found a loose heat shield on my up pipe I thought I found it but no dice. My upgrades are very similar ^^ stage 2 pro tune with a turbo back exhaust (catless) and spt intake. I just had my 60k service and again they couldnt find anything wrong. I will also continue the search for this annoying issue and post when I find it.
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Old 03-14-2013, 10:03 PM   #23
Thunderbird28
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Well I just ordered a new rear o2 sensor. So hopefully that will at least fix my problem of running at 13.7 afr all the time and hopefully the hesitation as well. If this doesnt work, Ill be checking fuel pressure, then probably replacing the front o2 if it still isnt fixed. Just out of curiosity, could running a catless exhaust burn up the sensor faster for some reason?
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Old 06-21-2013, 01:30 PM   #24
dietzy5
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any update on this?
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Old 06-21-2013, 01:59 PM   #25
section8suby
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Well after having the knock sensor retorqued the problem has come back but never as bad as it used to be. Im still trying to pin point the cause of it but Im leaning more towards bad fuel... Even though I buy Chevron and shell only. I have watched the fine knock, feed back knock and the DAM. Before the sensor was looked at my knock readings were really high and had caused the DAM to 0 out. Now it has stayed at 1.
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