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Old 07-18-2009, 06:46 PM   #1
Suby Noob
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1994 Toyota Pick-Up
2009 DGM WRX Sedan

Default 09 WRX Hesitation - Logs Inside - Need Help

I posted awhile back when I first purchased my vehicle because I was feeling a slight hesitation in first gear around 2500-3000 RPMs under normal driving conditions (ie. Not WOT). It felt as though the engine would just shut off for a split second. I was informed by the powers that be (Unabomber), that it had something to do with the Open Loop/Close Loop programming implemented in all 2006 vehicles and onward (minus one vehicle of the manufacturers choosing for each model year that obviously being the STI). It has something to do with emissions I believe. Anyways, I was wondering if it is possible to see what is going on from the logs below. I was hoping someone with more knowledge could decipher this log. I was also wondering why the fuel injectors basically cut out at around 4.5 seconds into the log. That was where I shifted, but I thought the injectors just dropped to 1 or 2 percent when shifting like they do under idle. My only guess when it comes to the hesitation is the 0 for Fuel Trim (Short) at 2.25 seconds. I dont understand what the difference is between Fuel Trim Short and Fuel Trim Long; if someone wanted to explain that, I would greatly appreciate it. If not, there is always the search button... Oh, and the vehicle has is running the stock map, no other mods. Just an AP v2 married to it. Thanks.



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Old 07-18-2009, 08:17 PM   #2
424wrx
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did you try one of the accessport maps yet? from what ive seen the 08 and 09 wrxs had these hesitation issues. mine had it as well.flashed the perrin map and hesitation was gone for me.just a though. get rid of the stock tune. they stink!
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Old 07-19-2009, 12:33 AM   #3
Suby Noob
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2009 DGM WRX Sedan

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Yea, that is what Ive heard - the stock maps blow. I was gonna hold out a little longer. Some of the 09s were having spun bearing issues, so I was gonna wait till 12k till I did anything other than a stock map. I am looking forward to stage 1.
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Old 07-22-2009, 08:47 PM   #4
Boosted WRX STi
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Fuel trims deal with the amount of fuel being injected and the resulting AFR. If the car is not hitting its desired AFR - it only checks this in closed loop - it adjusts the injector pulse width, and consequently varies the amount of fuel being injected to hit as close to its target AFR as possible. Depending on how low or how high it is over the target, it will add or subtract a percentage of fuel (pulse width).

As for short and long fuel trims, I believe "short" refers to the immediate trend in the injector pulse width, while the "long" is the average change. I am not 100% positive on these difference though.

As for your hesitation, I am not sure. I am pretty sure injectors do go limp - 0 - when your not on throttle, and in between shifts, I would assume your not on the throttle, so that seems normal. The hesitation could be the dreaded CL/OL transition that has plagued so many MY07+ vehicles.
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Old 07-22-2009, 09:15 PM   #5
nkodemus82
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Suby Noob, Regarding those spun bearing issues, I was one of the people who got a shiny new engine in my 09 WRX. That has been pretty well narrowed down to a material/assembly defect in the July, August and a very few early September builds. If you are 2009/Oct or later (check the vin plate on the door jamb) you should be pretty well in the clear, according to statistics from reports here. http://forums.nasioc.com/forums/show...php?p=27518933(And a list compiled by Tea Cups, here http://forums.nasioc.com/forums/show....php?t=1695936)

Just in case you are in the safe range... less need to be paranoid about spinning a rod bearing. I spent a lot of time looking over my shoulder until it happened and I don't wish that paranoia on anyone.

Regarding fuel trims, scantool.net has this to say at https://www.scantool.net/support/ind...kbarticleid=28
Quote:
Fuel Trim refers to feedback adjustments to the base fuel schedule.

Short Term Fuel Trim refers to dynamic or instantaneous adjustments (i.e., during braking/accelerating).

Long Term Fuel Trim refers to much more gradual adjustments to the fuel calibration schedule than short-term trim adjustments. Long term adjustments compensate for vehicle differences and gradual changes that occur over time.
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Old 07-23-2009, 07:44 PM   #6
Suby Noob
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2009 DGM WRX Sedan

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nkodemus,

Thanks for the info. I keep up to date on the two 09 engine problem threads. The thing that scares me is the two failed engines for sept. The last 6 of my VIN is 506XXX. So... theoretically I should be out of the range, but there is only roughly 3000 separating me from the failed motors. I think I will wait just a smidge longer. As for the hesitation, I think it probably is the OL/CL delay. I am really looking forward to the smoothness I have heard others say about Stage 1.
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Old 08-03-2009, 12:09 AM   #7
SargeBT
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This brings up a question for me. I've never seen a REAL answer on AP tunes being detected when it comes to warranty claim time.

Some folks say "Nope they can't detect it, if you unmarry it".

Some folks say the ECU has a reflash counter and Subaru can tell if the ECU has been flashed.

I really haven't seen any hard info to back up either claim, or any threads from people saying their warranty claim was denied because their AP was detected after unmarrying.

Regardless. The way I see it is IF they have a flash counter, then you flashed your ECU with the "stock" map when you installed the AP. Therefore, there is NO difference between flashing it with Cobb Stage 1 and unmarrying in the event of requiring warranty and flashing it with stock and unmarrying.

Flash the Stage 1 and enjoy is my 2 cents.
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