"Studdering" Fix Released

Im on the northshore of Boston, MA and today the weather dropped from yesterdays 90+ and humid, to like 75-77 with very little humidity. Also, I normally fill with Mobil 93 gas, and yesterday I tried Sunoco Ultra 94. Seems to be a bit better this morning, however havent had much time to experiment with it.......I will later though.

Do any of you think the higher octane will produce a better ride.......i know there has been some debate on the gas issues as well (i.e) top tier, 89,91, etc.

Joe

Yup, stevecamp I've got a 5EAT and the studder is non-existant at ambient temps of 60F or below but once it starts hitting 80F and above, you can easily induce it.

Well i'm thinking seriously about going the Cobb AP route in the not too distant future so hopefully that will help any issues

also............It just seems so odd that really humid and hot weather will cause such an issue with the turbo in our LGT's. Never heard of other turbo's having such a defined problem...

maybe its me?

dark_rex : the ECU tuners tune the actual A/F ratios and so they aren't depending on Subaru's stock A/F map to give them more fuel. Any power increases from the ECU tuners comes from raising boost, but correct me if I'm wrong.

That's what I'm saying. the tuners are able to lean the a/f out substantially enough to get to a 50hp gain. it's probably not coincidence that after you're reflashed and 50hp to the good, you also no longer have the studder.

dR

So the absurd part of my conversation with the service manager comes when he asks me what grade of fuel I’m pumping into the car. Only the best, “93 Octane” says I. “Well” says the service manager, “my tech sniffed a sample of the fuel in your tank while performing your injector flush, and he thinks you got a bad tank of gas, which could also promote the acceleration surging you are reporting, you might want to change stations where you purchase fuel”.

That's what I'm saying. the tuners are able to lean the a/f out substantially enough to get to a 50hp gain. it's probably not coincidence that after you're reflashed and 50hp to the good, you also no longer have the studder.

 

dR

The increased power comes from increasing the boost, not changing the A/F ratio. Also, I have Cobb stage 1/91 and, while the stutter is improved, it's not gone completely.

Well, it's the second day of cooler (70's) air here in Michigan and the bucking has vanished. We had a long stretch (3 weeks) of 90 degree very humid weather and it bucked the whole time. Drove it a bit yesterday and it was VERY mild. Drove her to work today and could not get her to buck at all. Oh and must mention how much faster she feels in this cool dry air. Love this weather...

+1

I've said all along that mine didn't start surging until summer rolled around. Hot weather makes it bad, hot weather + AC on makes it worse.

It's barely noticeable in sub 80° temps.

Here is my experience FWIW

Monday July 25th I scheduled dealer appt for studdering issue

Facts:

Car has studdered and hesitated since new

Build date 06/04 Legacy GT MT wagon.

18230 studdering miles

ECU sent out for reflash - 3 days turnaround - despite being told initially it would be 8 days.

Findings

Has definately improved situation, nowhere near as bad as before, but still present. Especially in 3rd and 5th gear medium acceleration from 2500rpm.

I'm not sure i could recommend it as a completely worthwhile fix - but if its available, my motto is to take it.

Here is my experience FWIW

 

Monday July 25th I scheduled dealer appt for studdering issue

 

Facts:

Car has studdered and hesitated since new

Build date 06/04 Legacy GT MT wagon.

18230 studdering miles

ECU sent out for reflash - 3 days turnaround - despite being told initially it would be 8 days.

 

Findings

Has definately improved situation, nowhere near as bad as before, but still present. Especially in 3rd and 5th gear medium acceleration from 2500rpm.

 

I'm not sure i could recommend it as a completely worthwhile fix - but if its available, my motto is to take it.

How many miles have you put on since the "fix". Simply resetting the ECU seems to make it better for a little while on mine but then it comes back. Please let us know if it gets worse again as you put more miles on.

Got my car back today. Too early to tell how well the fix worked.

I did get some info from the service rep. The fix is not designed to eliminate

the problem completely according to the district manager. It will fix about 70%

of the problem in most cases. They reduced the time to calculate some parameters

which will remove some of the studder, but not all.

He also mentioned something about getting through EPA quickly.

/t

Does anybody know if after Stage I or even II does it get better with or without the fix?

Any input pls???

Tx

Flavio Zanetti

Boston, MA

The increased power comes from increasing the boost, not changing the A/F ratio. Also, I have Cobb stage 1/91 and, while the stutter is improved, it's not gone completely.

increasing the boost DOES change the A/F ratio. more boost = more air = more lean.

dR

increasing the boost DOES change the A/F ratio. more boost = more air = more lean.

 

dR

In a carbureted (or mechanically fuel-injected) engine this would be true, but the MAF should detect the extra air coming into the system and adjust the fuel delivery to achieve the mapped A/F ratio.

DKB

increasing the boost DOES change the A/F ratio. more boost = more air = more lean.

 

dR

Ummmm. I think you're confused. Typically when increasing boost, tuners will alter the fuel tables to add more fuel to specifically avoid a lean condition. A/F ratio and boost target tables can be controlled and manipulated independently from each other.

If you were silly enough to increase boost without also increasing fuel delivery, the engine would, in fact, run lean... At least for a few minutes before your pistons burn.

Back on topic:

Sounds like we've had a couple of semi-success stories with this "fix". Anyone else had any luck with it??

In a carbureted (or mechanically fuel-injected) engine this would be true, but the MAF should detect the extra air coming into the system and adjust the fuel delivery to achieve the mapped A/F ratio.

 

DKB

Actually, you can also control your A/F ratio on a carbureted engine, you just have to re-jet the carburetor.

It is true that you can't do it electronically like you can in an EFI equipped car. You'll also get more fluctuation in your A/F ratio since the system can't monitor and make real-time adjustments.

Picked up mine today from the reflash and now all I notice is slight turbo lag off-boost. No stutter, stammer, or bucking. I put it into all of the profiles that used to ellicit the condition in the past, e.g.,

• 2500 rpm and off accelerator and then back on the accelerator in almost any gear but 1st at about 50% throttle position - nothing - just smooth acceleration. (no stutter),
  
• cruising along at 3,000 rpm, drop off the accelerator to about 2200-2500 rpm and give it about 50% throttle - still smooth acceleration (just a hint of turbo lag) but definitely no stammer,
  
• 2nd gear rolling along at low rpm and add about 50% throttle, moves off with no hint of hesitation of bucking
  
• Up a grade in 4th at 3000 rpm, adding in throttle to accelerate, just unwinds smoothly and unbelievably fast.
  

Temps were in the 85 - 95 F range, plenty of heat soak from sitting in traffic and yet still no sign of the previous bedevilment. Honestly, the car was sitting in heavy, hot traffic with the AC on the whole time so I'm fairly certain it was operating normally through the entire range.

Drivetrain just feels and acts smoother all the way around. Car is definitely faster, like "holy afterburner Batman, this thing is waaaay fast"... much faster than I ever noticed before and this is at 11,000 miles. Someone pinch me quick so I can make sure I'm really not sleeping, the car feels that different. I can't imagine what this car would be like with a Stage 1 or State 2 setup.

Don't know if anything will change as the ECU re-learns or whether they pulled what they needed out of my previous tables or not and just loaded those pieces back in. I hope this fixes it.

BTW - for those who are getting this done, take your extra remote fob along and they'll reprogram it for you too.

HTH

SBT

^^^^

Great news!!! Thanks for the update!

 

BTW - for those who are getting this done, take your extra remote fob along and they'll reprogram it for you too.

 

HTH

 

SBT

Sorry, I'm not sure what do you mean by this... Why would you need your extra remote reprogrammed?

^^

lol for real! what the hell is that all about? another problem??...

^^

lol for real! what the hell is that all about? another problem??...

Not another problem. Just that when you get your ECU reflashed, the security system, which is integrated into the ECU, no longer recognizes your remote fobs. So, just take them with you when get your ECU reflashed and the dealer will reprogram the system for you. Or, you can do it yourself, following the instructions in the manual.

The dealer asked me to bring my extra fob when I came to pick up the car, so they could program both at the same time. Thought it was cool of them to think of that and call me.

Incidently, went for an 80 mile run up the coast for dinner tonight and in and out of traffic the car was smoooooth. My wife even commented on how smooth it felt and if she notices something like that, it is definiitely something out of the ordinary. I just couldn't get over how much oomph the car had, even at lower rpms in 5th. Nary a hiccup the whole drive

SBT

^^

Excellent!

Keep us updated and let us know if things change much in the next 1000 miles or so.

Picked up mine today from the reflash and now all I notice is slight turbo lag off-boost. No stutter, stammer, or bucking. I put it into all of the profiles that used to ellicit the condition in the past, e.g.,

BTW - for those who are getting this done, take your extra remote fob along and they'll reprogram it for you too.

 

HTH

 

SBT

Thanks, SB!!

btw, what was the build-date of your car? I haven't had much bucking, but if it can make mine feel even teh faster.. :-)

Actually, maybe everyone who's qualified for the fix could post their build-time? We bought our Wagon in January '05, haven't checked build-time yet.. Just wondering if we qualify or not..

HV