03 legacy N/A stumbling acceleration/bucking
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This is a discussion on 03 legacy N/A stumbling acceleration/bucking within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I have a 03 legacy L. Bought a couple months ago, certified pre owned from a subie dealer. Just had ...

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    03 legacy N/A stumbling acceleration/bucking

    I have a 03 legacy L. Bought a couple months ago, certified pre owned from a subie dealer. Just had the 60k service done on it, all service records and everything was done according to the service schedule if not sooner. Happened a total of 4 times since I've bought the car, in 2nd or 3rd gear (MT) after the clutch it released, I will give it gas and the car will start violently bucking and I have to push in the clutch and release it to stop the bucking. Other times (happens more often than the bucking) in the same scenario clutch is out, I gas it and it hesitates like the rpm needle will bounce up/down then it goes or is slow to react. I've changed the oil every 3k miles if not less using Mobil 1 full synthetic, tranny/diff oil was changed 100 miles before I purchased it, there are no CELs etc and these symptoms are random and don't occur every time. I've taken it to 2 different subaru dealers a total of 4 times now, every single time they take it for a drive and can't reproduce the issue and say there is nothing wrong with the car. The current dealer that has my car now has had it for 2 days and has been driving it saying they can not reproduce the issue and there is nothing more they can do. I have the SAS which expires March of 08, any other ideas of what I can ask them to do or ask them to check that would potentially help in diagnosing this issue?

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    Moderator YBNormal07's Avatar
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    Have you asked the dealer if there are any TSBs that affect your year/model?

    You can research TSBs here and try to find something similar.
    http://www.scoobymods.com/forums/arc....php/f-82.html

    "bucking" can be caused by a number of items, but I would say it would likley be the ECU AFR map. I'm assuming you have the motor and tranny mounts checked?
    tEh PriUs=teH faSTah!@@!
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    Quote Originally Posted by YBNormal07 View Post
    Have you asked the dealer if there are any TSBs that affect your year/model?

    You can research TSBs here and try to find something similar.
    http://www.scoobymods.com/forums/arc....php/f-82.html

    "bucking" can be caused by a number of items, but I would say it would likley be the ECU AFR map. I'm assuming you have the motor and tranny mounts checked?
    yes, they were inspected before I bought the vehicle by Worldone performance. Its the same type of bucking if you were in too high of a gear for the speed you were going, say being in 5th at 20mph and trying to gun it. It was really bad to the point it could of caused an accident if there were other people around because the entire car was bucking so hard it was pushing/throwing me back hard.

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    Moderator YBNormal07's Avatar
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    Might need to have the MAF cleaned, or possibly injectors/throttle body cleaning. Shouldn't need it on that new of a car, but these are also items that could cause "bucking". Check out the TSBs I linked also.
    tEh PriUs=teH faSTah!@@!
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    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
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    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

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    thanks, I checked the TSBs but didn't find anything relating to my issue. The 03 legacys have a MAP sensor not a MAF, I've never had a car with a MAP sensor so I'm not sure exactly how they work and how to clean it if I need to. The injectors were also cleaned by the dealer as part of the 60k service.

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    Quote Originally Posted by infox View Post
    thanks, I checked the TSBs but didn't find anything relating to my issue. The 03 legacys have a MAP sensor not a MAF, I've never had a car with a MAP sensor so I'm not sure exactly how they work and how to clean it if I need to. The injectors were also cleaned by the dealer as part of the 60k service.
    from what your saying its possible its a pressure plate issue..if it isnt evenly applying pressure to the disc then you could get a nasty shudder from that..havent seen any be intermitent problem but i have seen them fail and cause a issue similiar to what your saying...thats my best guess without actually seeing the car
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    feel free to pm me with any questions..

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    Moderator YBNormal07's Avatar
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    Quote Originally Posted by subarutech View Post
    from what your saying its possible its a pressure plate issue..if it isnt evenly applying pressure to the disc then you could get a nasty shudder from that..havent seen any be intermitent problem but i have seen them fail and cause a issue similiar to what your saying...thats my best guess without actually seeing the car
    I considered that also, but as you said, it would be a steady problem, not intermittant.

    I'm still going with the auto fire triangle...it's either air, gas, or spark in nature. A data logger would do wonders for cases like this.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

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    Quote Originally Posted by YBNormal07 View Post
    I considered that also, but as you said, it would be a steady problem, not intermittant.

    I'm still going with the auto fire triangle...it's either air, gas, or spark in nature. A data logger would do wonders for cases like this.
    thanks, they said they were actually going to go out with another tech tomorrow (today) and run a data logger to see what they can tell from that.

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    just thought I'd give a update, not sure if you guys are familiar with the ECU reflash from subaru on the LGT's but its also available for the older LGTs and base model legacys which is supposed to fix this issue and also make the car smoother throughout the whole power band. The dealer reflashed my ECU with the updated firmware and said its running good so I'll see when I pick it up tonight, also I found out the ECU & catalytic converter are required by federal law to be warrantied by the manufacturer for 8yrs or 80,000 miles which means I didn't have to pay the deductible on my warranty which makes me happy

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    Registered User SubyPsycho's Avatar
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    Just my $.02 - I know someone who had a Mazda doing this. It turned out to be a crack in the intake.

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    seems like the ecu reflash took care of the issue, overall the car has a lot more throttle response seems a bit quicker on the butt dyno and is smoother overall throughout the entire powerband.

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