07 Legacy Spec.B - Jerky Acceleration

[Lothar of the Hill People]

I have a 9-month-old 2007 Subaru Legacy Spec.B than has been
accelerating somewhat choppily ever since I bought it. At first I
just wrote it off as normal turbocharger lag, but lately I have been
wondering if this is indeed normal.

What happens is that if I shift up into a gear (e.g. shifting from 1st
into 2nd) and then I floor the accelerator, as if I am trying to pass
somebody, instead of getting a nice smooth power flow, it accelerates
a bit jerkily and hesitates about 3 times before it becomes smooth.
It's a subtle jerkiness (not like the whole car is shaking), and feels
like a throttle issue rather than, for example, clutch slippage (but
who knows). I have noticed this issue in both Sport and Sport Sharp
modes, but most frequently in Sport Sharp because that's where I
usually have it set.

Can anybody tell me if their own Spec.B behaves similarly, or let me
know if this sounds like something is wrong?

Thanks.

 

[Bugalugs]

I have a 9-month-old 2007 Subaru Legacy Spec.B than has been
accelerating somewhat choppily ever since I bought it. At first I
just wrote it off as normal turbocharger lag, but lately I have been
wondering if this is indeed normal.

What happens is that if I shift up into a gear (e.g. shifting from 1st
into 2nd) and then I floor the accelerator, as if I am trying to pass
somebody, instead of getting a nice smooth power flow, it accelerates
a bit jerkily and hesitates about 3 times before it becomes smooth.
It's a subtle jerkiness (not like the whole car is shaking), and feels
like a throttle issue rather than, for example, clutch slippage (but
who knows). I have noticed this issue in both Sport and Sport Sharp
modes, but most frequently in Sport Sharp because that's where I
usually have it set.

Can anybody tell me if their own Spec.B behaves similarly, or let me
know if this sounds like something is wrong?

Thanks.

Have you thought about a plug momentarily fouling with too much gass
when you floor it?

That's what mine feels like

 

[Lothar of the Hill People]

Have you thought about a plug momentarily fouling with too much gass
when you floor it?

That's what mine feels like

That sounds like as reasonable explanation as any, but what would
cause such a thing to happen in a brand-new vehicle?

Anyway, I posted this same question on the forums at
http://legacygt.com/forums/ and apparently this is a very common
complaint, about something that people have been referring to as
"stuttering" or "studdering." It sounds like the problem might be
caused by a fault in the ECU program, though I'm not certain yet that
my problem is exactly the same one they're describing.

 

[Bill Bradley]

I have an 07 Legacy 2.5 GT sedan with automatic, and, I've felt a slight
"hesitation" or something, almost like the power shutoff, then back on,
while accelerating a few times. It's almost like you ran over a slight bump
in the road, and, the car kinda slows then speeds back up quickly.

I know it's a different engine, but, maybe it's something to do with the
4-cylinder or turbo?

I also, after a while, get a hesitation when trying to quickly accelerate,
like when trying to pass someone. I am just telling Subaru to reset the
transmission every time I go in for service, so that it "learns" all over
again, as, that seems to fix it. This is different from the other issue.

 

[Dee]

I have a 9-month-old 2007 Subaru Legacy Spec.B than has been
accelerating somewhat choppily ever since I bought it. At first I
just wrote it off as normal turbocharger lag, but lately I have been
wondering if this is indeed normal.

What happens is that if I shift up into a gear (e.g. shifting from 1st
into 2nd) and then I floor the accelerator, as if I am trying to pass
somebody, instead of getting a nice smooth power flow, it accelerates
a bit jerkily and hesitates about 3 times before it becomes smooth.
It's a subtle jerkiness (not like the whole car is shaking), and feels
like a throttle issue rather than, for example, clutch slippage (but
who knows). I have noticed this issue in both Sport and Sport Sharp
modes, but most frequently in Sport Sharp because that's where I
usually have it set.

Can anybody tell me if their own Spec.B behaves similarly, or let me
know if this sounds like something is wrong?

Thanks.

This is a known issue with the 07 STi, and I just read that it MAY extend
to the 07 Legacy Spec.B also. It has to do with the ECU mapping, which
apparently Subaru had to radically modify to meet the new emissions
standards for 2007. Subaru released an ECU reflash for the STi, but it
does not really fix the problem.

You might want to check out the online forums.

http://forums.nasioc.com/forums/
http://www.iwsti.com/forums/
http://www.legacygt.org/forums/

Dee

 

[Lothar of the Hill People]

This is a known issue with the 07 STi, and I just read that it MAY extend
to the 07 Legacy Spec.B also. It has to do with the ECU mapping, which
apparently Subaru had to radically modify to meet the new emissions
standards for 2007. Subaru released an ECU reflash for the STi, but it
does not really fix the problem.

You might want to check out the online forums.

http://forums.nasioc.com/forums/
http://www.iwsti.com/forums/
http://www.legacygt.org/forums/

Dee

I had actually already checked out the forums at
http://legacygt.com/forums/ (which I guess is a different website than
the URL you posted above) yesterday, after I posted my question here,
and one of the replies I got said basically the same thing you just
said. He elaborated that the problem is shared between the 2007
Legacy Spec.B and the STi because they share the same "new" ECU.

Can you elaborate what you mean when you say the ECU reflash doesn't
really fix the problem? I read a few people post that they had a
reflash done and it did fix the problem (though only temporarily for
some people).

 

[Lothar of the Hill People]

I have an 07 Legacy 2.5 GT sedan with automatic, and, I've felt a slight
"hesitation" or something, almost like the power shutoff, then back on,
while accelerating a few times. It's almost like you ran over a slight bump
in the road, and, the car kinda slows then speeds back up quickly.

I know it's a different engine, but, maybe it's something to do with the
4-cylinder or turbo?

That sounds somewhat similar to what I'm experiencing, but I'd
describe it more like a very quick stutter every time I try to
accelerate hard. On my car though, I don't think it's a transmission
issue. I have a 6-speed manual. Like the other poster said, it
appears to be a poorly-programmed ECU. My dealer told me today that
there is an ECU update available for this issue, so I'll try that out
and see if it fixes it.

 

[Dee]

I had actually already checked out the forums at
http://legacygt.com/forums/ (which I guess is a different website than
the URL you posted above) yesterday, after I posted my question here,
and one of the replies I got said basically the same thing you just
said. He elaborated that the problem is shared between the 2007
Legacy Spec.B and the STi because they share the same "new" ECU.

Can you elaborate what you mean when you say the ECU reflash doesn't
really fix the problem? I read a few people post that they had a
reflash done and it did fix the problem (though only temporarily for
some people).

I wrote that it doesn't really fix the problem because from reading the
forums it seems that for the majority of the people the symptoms return.
I'm not sure why that happens; perhaps it has something to do with the ECU
"relearning" or reverting. There are a couple of people who say they've
never experienced the hesitation/stuttering, but they are in the minority.

For me, the reflash smoothed things out for a couple of days, and then it
reverted back.

A couple of things that work for me: keep the revs up and in the boost zone
so that when you need the turbo it will respond immediately. Also, turn
the A/C on - people are finding that this somehow reduces or eliminates the
hesitation. This summer I have had the A/C on constantly and the car does
seem to run better and smoother.

There is a poster on IWSTI who swears up and down he has never experienced
the hesitation, but he lives in Miami, so you can imagine he's probably
never driven the car without the A/C.

Dee