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Old 06-23-2009, 06:55 PM   #1
mikehoyer
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Default Stock 07 WRX Wagon Intermittent Bucking Stumbling/Hesitation/Bucking

So...

Stock 2007 WRX Wagon

47,700 miles now on the car. (9/9/09)

I've been having intermittent engine problems with my car since I bought it new. The car will start to act up every few months and then the problem will go away. The problem seems to be mainly in the 2500-3000RPM range. I'll be cruising on the highway, and the car will start to buck when going up a small hill. The problem will persist for an hour or so, and then go away.


I've brought my car into the dealership for the problem. They datalogged the car while it was "acting up", and there were no problems detected from any sensor while the car was acting up.

So far, what has been done:
Flashed with a different map
Cylinder #3 was misfiring so replaced all the plugs
Removed and inspected the intake and exhaust pipes.
Used 440 fuel injector cleaner
Dry Gas
Had an EFI treatment done with BG products.
Dealership cut a hole in the fuel sock.
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Last edited by mikehoyer; 02-18-2010 at 05:48 PM. Reason: Updates
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Old 07-10-2009, 04:21 PM   #2
mikehoyer
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I brought the car back to the dealership on Monday. Subaru wanted the tech to do some more datalogging on my car. I got word from Subaru today that they think the problem was due to carbon buildup. They are saying that the ethanol in fuel now causes lots of problems with the EFI system, and I should have an EFI maintenance done for $115. Whatever was stuck somewhere in my engine has aparantly let go, and it's working fine now.

Last edited by mikehoyer; 02-18-2010 at 05:49 PM.
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Old 07-10-2009, 04:35 PM   #3
Bullwinkle1983
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Drive it harder more often. If you go WOT more often, you'll be less likely to have valve/misfire/buildup issues.

Seriously.
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Old 07-10-2009, 05:48 PM   #4
Lboogie
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Maybe they just reset the ECU by unplugging the battery. So the issues might come back after a couple hundred miles.

The ethanol angle sounds more like dumb dealership talk. I've run E85 in my tank (4-5gallons mixed with remainer of 91 in tank) many many many times...no misfiring. I also am close to 50k mi, no carbon buildup issues.

Not only that but we have the crappiest 91octane fuel here in California, don't know what its like in your neck of the woods or if you are lucky to have 93oct at the pump.
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Old 08-18-2009, 09:05 PM   #5
mikehoyer
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Update:

I think the EFI treatment worked because my car feels more powerful overall. My guess is that I was getting really ****ty gas when I lived in Philadelphia. I think I'll get another EFI treatment in a few thousand miles to get rid of anything that might be lingering on the valves.

Last edited by mikehoyer; 02-18-2010 at 05:50 PM.
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Old 08-23-2009, 05:10 PM   #6
mikehoyer
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The dealership told me to bring the car in while it's acting up. The problem is that I'm usually on a long trip while the problem is happening.

Last edited by mikehoyer; 02-18-2010 at 05:51 PM.
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Old 08-24-2009, 12:49 AM   #7
iheartscooby
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Sounds a lot like the 07 STI ECU problem. Only fix for me was a tune.
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Old 08-24-2009, 02:14 AM   #8
kh15
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but what is the exact cause? ie. what tables need to be adjusted?
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Old 08-29-2009, 04:24 PM   #9
mikehoyer
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Update:

SOA recommends that I let the dealership try to recreate the problem I'm having. I'm leaving the car with the dealership for a few days while I'm on vacation. SOA wants to datalog the car while it's acting up. The problem is that the dealership already datalogged the car while it was acting up and there were no visible problems from any sensor. This feels like I'm just jumping through another hoop, but that's all I can do right now without suing.
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Old 08-29-2009, 05:11 PM   #10
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I suspect a bad coil pack.
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Old 08-29-2009, 06:32 PM   #11
afviper
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I am not sure how the lemon law works but you may want to look into it.
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Old 09-09-2009, 05:13 PM   #12
mikehoyer
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Update:

I dropped off my car on 9/3/09 at the dealership. Luckily the car was bucking when I dropped it off. The service group leader drove the car with the service manager and myself in the car. For whatever reason, they did not datalog the car while it was acting up. The two of them decided that the fuel sock was collapsing, and that was causing the bucking.

I returned on 9/9/09 to pick my car up. They cut a hole in the fuel sock to let more fuel get to the pump. I told them the last time I brought my car in while it was acting up there was no problem with the fuel pressure. They told me to bring the car in again when it was acting up and they would replace the fuel pump. I told them I was not happy with that resolution, and I was going to speak to SOA. I spoke with SOA, and SOA told me the same thing the dealership did. I told SOA I'm done working with them, and they can talk to my lawyer.

Let the fun begin...
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Old 09-09-2009, 07:59 PM   #13
kpluiten
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The fuel sock is there for a reason! How is cutting a hole in it any sort of resolution?!

It's there to provide filtration of large particles that may damage the fuel sending unit (fuel pump). With a hole in it, it's now possible for some piece of crap to be easily sucked up and lodged in the pump unit. While this is an outside chance, it's at least enough of a chance that Subaru felt the need to include the sock in the first place.
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Old 09-09-2009, 08:23 PM   #14
Krang
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Did the dealership really cut a hole in your fuel sock? Really? Because they just voided their own warranty, lol.
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Old 09-10-2009, 08:12 PM   #15
mikehoyer
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Quote:
Originally Posted by kpluiten View Post
The fuel sock is there for a reason! How is cutting a hole in it any sort of resolution?!

It's there to provide filtration of large particles that may damage the fuel sending unit (fuel pump). With a hole in it, it's now possible for some piece of crap to be easily sucked up and lodged in the pump unit. While this is an outside chance, it's at least enough of a chance that Subaru felt the need to include the sock in the first place.
Quote:
Originally Posted by Krang View Post
Did the dealership really cut a hole in your fuel sock? Really? Because they just voided their own warranty, lol.
Yeah, it's pretty ridiculous. The fuel sock increases the inlet surface area of the pick-up tube so debris can't block fuel flow. I was pretty dumbfounded when they told me what they did.

Last edited by mikehoyer; 02-18-2010 at 05:53 PM.
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Old 09-19-2009, 07:24 PM   #16
mikehoyer
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Update:

I was surprised when my car started bucking on the highway today. I was sure the hole they cut in the fuel sock would have fixed the problem.

Yeah...
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Old 09-24-2009, 02:42 PM   #17
Daluv
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Im chasing down the exact same problem on my 06 STi... cahnged the 02 front sensor and the PCV valve .. no luck
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Old 09-24-2009, 07:18 PM   #18
bcblues
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I'm still thinking coil pack......
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Old 09-25-2009, 07:10 AM   #19
Daluv
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How can you explain that the coil pack can failed at lower rpm and not at high rpm?

Also, I dont see any misfire in my logs...

Quote:
Originally Posted by bcblues View Post
I'm still thinking coil pack......
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Old 09-25-2009, 09:21 AM   #20
DCales
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My 06' would do something similiar to this before purchasing an accessport. I really think that you should look into either an AP or having it dyno tuned. I replied to another post about a car that runs poorly intermittently and rec. the same thing. They may be able to find something that is not setting a DTC and improve the drivability.

On a side note the EFI system cleaning most dealers sell is a joke. Ive been a tech at several dealers and will say that our cars should not have a cabon issue with such low miles miles esp. when using 91 or 93 octane fuels. At best they wiped out the throttle body, added fuel treatment, and ran cleaner through the intake. I personally own the justice brothers fuel induction tool and paid $35 for it. I can get the cleaners for $20 at the local parts dept and do it myself for much cheaper.

Good luck with getting this figured out let us know if anything works for you.
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Old 09-25-2009, 12:55 PM   #21
bcblues
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Intermittent missing always triggers a red flag for me on the coil pack. If you have ruled out a clogged injector, that is still my best guess....

Quote:
Originally Posted by Daluv View Post
How can you explain that the coil pack can failed at lower rpm and not at high rpm?

Also, I dont see any misfire in my logs...
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Old 09-25-2009, 01:24 PM   #22
Daluv
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ok I understand that. I am only trying to understand the logic behind it...

Quote:
Originally Posted by bcblues View Post
Intermittent missing always triggers a red flag for me on the coil pack. If you have ruled out a clogged injector, that is still my best guess....
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Old 12-19-2009, 09:08 PM   #23
mikehoyer
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Quote:
Originally Posted by DCales View Post
Good luck with getting this figured out let us know if anything works for you.
I'm selling the WRX. Anyone interested? It hasn't had any problems in awhile. I'm sure it's any easy fix if you know where to look. I just don't have the money to fix the car right now, and I could use the money for other things.

07 OBP WRX Wagon
54K miles
Urethane Rally Armor mud flaps
SOLD

Located in New Hampshire
Live Free or Die

Last edited by mikehoyer; 02-18-2010 at 05:54 PM.
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