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04-30-2010, 03:42 PM | #1 |
Scooby Newbie
Member#: 174095
Join Date: Mar 2008
Location: SoCal
Vehicle:2011 EVO X MR White |
4EAT Problem on 2008 Impreza 2.5i
Hi all,
I've got a weird problem on my other car, and it has been there since day 1 (Fall, 2007). But I didn't think much about it 'till recently I was driving the car again after letting my brother drive it for a while. I'm going to describe the scenario to you guys step by step, and hopefully someone can confirm whether this is a problem, or all 4EAT does this... Say, I'm going down the street approaching a stop sign at 30 mph in 3rd gear (I'm using the manual function here so I can get a read-out of the gear). As I get closer, I begin to depress the brake pedal. As the car slows down, it automatically shifts into 2nd gear. As it slows down some more, nearly coming to a stop, the engine revs itself. At this point, I can feel the car accelerate forward a tiny bit in a jerking motion. I can certainly feel the vibration from the brake pedal. About maybe half a second to a second later (when the vehicle speed is decreased some more), the car shifts itself into 1st gear. About a few milliseconds later, I'm at a complete stop. Whatever I just described can be reproduced nearly 100% of the time. And the jerking motion seems to have gotten worse. I have an appointment with local dealership this coming Monday morning to look at the car, and I'd like to get a heads-up on what potentially could be wrong. I don't know much about transmission (or car really), but it seems to me that the timing between the ECU-controlled shifting down to 1st gear and the ECU rev-match is off. This result in a pre-mature "rev-match" in second gear, which in a automatic with no clutch means forward acceleration. I will try to take some video of the dash after I get home today. Some things to consider: The brake pad was replaced before 30k miles with no hard driving at all. Rotor warped 3 times, so resurfaced 3 times. The thickness is about to warrant a replacement from Subaru. Both of these seem to point to an abnormal usage of brakes under normal circumstances. My brother's commute is about 10 miles each way on the 405 for those of you in SoCal. If you drive a Subaru with 4EAT, please let me know if this happens to you. Thanks so much. *EDIT* As promised, I recorded a short video of the tachometer as I drove around. The first section is done in the "Sport" mode, followed by manual gear selection, then lastly the "D." Note how the rev goes up as if the ECU is doing the rev-matching as it downshifts. But the problem is that it always rev-match premature to the downshift. So I end up jerking forward. It's difficult to record the jerking/acceleration, but it can certainly be felt with your butt on the seat.
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Last edited by A5un; 04-30-2010 at 09:44 PM. |
04-30-2010, 05:42 PM | #2 |
Scooby Specialist
Member#: 78408
Join Date: Dec 2004
Chapter/Region:
MAIC
Location: NoVA
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What part of Souther California are you from?
There's tons of good shops out here, search for "Subie Specialties". I recommend you have it looked at, because based on your description, it sounds like a trans issue. |
04-30-2010, 05:45 PM | #3 |
NASIOC Vendor
Member#: 136396
Join Date: Jan 2007
Chapter/Region:
MWSOC
Location: Minneapolis, MN
Vehicle:2020 STI, 2022 WRX |
Does it do this when you're in D or just in 3rd? It's normal for the car to down shift in 3rd it just shouldn't be able to up shift at all. 2nd and 1st are the only gears that shouldn't automatically change on you no matter what.
Mike |
04-30-2010, 06:15 PM | #4 | |
Scooby Newbie
Member#: 174095
Join Date: Mar 2008
Location: SoCal
Vehicle:2011 EVO X MR White |
Quote:
*Second thought*They're way too far in Monrovia...can't work out the car schedule if I need to go that far...Got any other reputable shop? I know Renner Motorsport near me, but they don't seem like they service automatic trannys...But I could be wrong. I was gonna try my luck there too anyways tomorrow... Last edited by A5un; 04-30-2010 at 06:24 PM. |
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04-30-2010, 06:19 PM | #5 |
Scooby Newbie
Member#: 174095
Join Date: Mar 2008
Location: SoCal
Vehicle:2011 EVO X MR White |
Mike, the 3rd gear is just an example for the sake of describing the scenario. I could have the car in full auto in "D," or sports mode, or manual gear selection mode (in gear over the first gear). As long as I need to make a stop where the vehicle speed approaches zero (when the ECU automatically shifts the car into first), this sudden rev will occur. This is also why I believe the ECU supplied rev-match and the gear change timing is off.
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05-03-2010, 11:44 PM | #6 |
Scooby Newbie
Member#: 174095
Join Date: Mar 2008
Location: SoCal
Vehicle:2011 EVO X MR White |
In case you guys are curous...which by the turn-out of the thread...it would appear that no one cares lol...
But I took the car in to Sherman Oaks Subaru today, and the lead mechanic told me that it's a problem with the car's transmission learning incorrect shift timing / habit. No idea how it can learn to rev before the actual shift, but whatever. They reset the computer and now it drives a lot better. Seems like the problem is gone all together. So if you think your 4EAT is really unsmooth, maybe get it checked out. *More Test Drive* Same problem...Sherman Oaks Subaru Fail! Last edited by A5un; 05-04-2010 at 01:53 AM. |
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