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Old 01-20-2009, 04:34 PM   #1
Eskimo1
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Default Fixes for 2000-3000rpm acceleration hesitation? (turbo)

You know it's bad when my wife even notices it.

Bone stock '05 Baja turbo 5MT 75k miles, but it's done it since we bought it with 61k... Not looking for more power necessarily, and certainly don't want her car to be louder... all my junk is plenty loud.

Is it tuning? Octane sensitivity? Crap-tasic exhaust flow?

I'm kind of a Scoobie-noobie, but building/working on/modifying vehicles of all sorts isn't.

TIA, and feel free to point me to a search if I missed it when doing my searches..

Thanks..
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Old 01-21-2009, 10:08 AM   #2
deadlydave
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Some usual culprits:
-Spark Plugs
-Plug Wires
-Air filter
-Fuel Filter

Is it an auto or manual transmission?
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Old 01-21-2009, 10:42 AM   #3
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I had the same issue with my 05 Subaru Sport(manual trans.), even after the plugs,wires,filters,and all the fluids were changed!...Oh, the dealership also reset the ECU which did'nt help!
Now I have an 06 Turbo(auto trans.) with the same problem- although its not as noticeable in the Turbo model. I wonder if its in the factory tuning?!?
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Old 01-21-2009, 11:17 AM   #4
moonzie
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I don't have any hesitation issues with my `04 AT turbo Baja when accellerating between 2-3k rpms. UNLESS my torque converter is locked up. When then TC is locked I get a subtle hesitating sensation when trying to accellerate - which is quite annoying but I've dealt with it since I bought it 2+ years ago.

When the TC unlocks from 4th and the power is unleashed well.. then it's just fun.
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Old 01-21-2009, 11:31 AM   #5
Eskimo1
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It's a 5-speed (5MT)... I suspect an auto's torque converter (when unlocked) would mask a huge part of this... moonzie's post kind of verifies this..

I should have mentioned, it's ONLY this band when accelerating moderately to hard. It idles great and pulls hard and clean after 3,000. Reminds me of compressor stall/surging..
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Old 01-21-2009, 11:53 AM   #6
deadlydave
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Quote:
Originally Posted by Eskimo1 View Post
It's a 5-speed (5MT)... I suspect an auto's torque converter (when unlocked) would mask a huge part of this... moonzie's post kind of verifies this..

I should have mentioned, it's ONLY this band when accelerating moderately to hard. It idles great and pulls hard and clean after 3,000. Reminds me of compressor stall/surging..
Any chance of a loose hose/clamp somewhere? I didn't notice the hesitation on my 04 turbo 5mt when stock. Now, it insn't quite stock anymore.

A guy on the local boards had this on his late 90's forester, he bought some MAF cleaner from NAPA and that helped some.
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Old 01-21-2009, 02:36 PM   #7
moonzie
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Quote:
Originally Posted by Eskimo1 View Post
It's a 5-speed (5MT)... I suspect an auto's torque converter (when unlocked) would mask a huge part of this... moonzie's post kind of verifies this..

I should have mentioned, it's ONLY this band when accelerating moderately to hard. It idles great and pulls hard and clean after 3,000. Reminds me of compressor stall/surging..
That's very interesting. So you're saying it does this in all gears as you run them up? And yes, an unlocked TC would mask it. hmm...

I'll have to try doing a moderate accelleration with the TC locked past 3000rpms; I rarely do any speeds over 75mph which pegs the tach right at 3k.

Also, the ECU is different for ATs and MTs. So that seems to cast some doubt over tuning. I dunno. I always thought it was something tuning related tho.. My TCU is actually pretty dumb. I am very convinced that it's also plagued by a bug that seems to have affected a small # of `04 foresters and Bajas that causes it to momentarily slip when downshifting from 3rd to 2nd along with a loud metalic ratchety sound on the upshift between 2nd and 3rd - but Subaru knows nothing about this. I read once where someone somewhere down in GA or AL or FL got a dealer to flash their TCU with an update that didn't pertain to their TCU and that completly fixed them but now for the life of me I can't find that info or the update code back on the web. It was buried somewhere deep on some other forums... blah.


anyways..
I've never touched my MAF, but it's definitly worth researching/trying. The original owner of my BajaT was a ranch owner so he probably used it in some pretty dusty environments before I ever bought it. Thanks for the tip deadlydave.

Last edited by moonzie; 01-21-2009 at 02:45 PM. Reason: tfcu
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Old 01-21-2009, 03:05 PM   #8
holland_patrick
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Sport dyno sheet.. there is a drop in the power band right there...


not sure why the t-bow would do it..
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Old 01-21-2009, 05:42 PM   #9
bulwnkl
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Cam phasing switchover point, perhaps?
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Old 01-21-2009, 06:05 PM   #10
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^ I'm thinking the same thing. My 04 does this as well. However, a previous tune had completely eliminated the hesitation. With the tune I'm running now it's back, but gas mileage is better and the power is more linear.
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Old 01-21-2009, 07:08 PM   #11
moonzie
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Quote:
Originally Posted by twheats1 View Post
^ I'm thinking the same thing. My 04 does this as well. However, a previous tune had completely eliminated the hesitation. With the tune I'm running now it's back, but gas mileage is better and the power is more linear.
Auto or Manual twheats?
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Old 01-21-2009, 07:29 PM   #12
Hawk296
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Sounds like it's an engine calibration thing. either something in the fueling or maybe an open loop/ closed loop transition or something like that.
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Old 01-21-2009, 07:36 PM   #13
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Manual ftw!
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Old 01-21-2009, 08:25 PM   #14
moonzie
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Well I took my MAF/AIT out tonight. There's one bulbus looking dark-red sensor that was entirely black with grime on one side and almost entirely black on the other. Cleaned it with Qtip and rubbing alchohol; it was filthy! Not sure if this was temp sensor or MAF. Peered further down the housing and saw 2 more sensors. I'm guessing these were the MAF sensor. They were much cleaner and I didn't pull any grime off of them at all.

Test drive revealed little if any difference on the highway while accellerating moderately with TC locked up. It seemed to feel more power responsive though when at lower speeds - but there's very good chance that was completely psychological.
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Old 01-21-2009, 08:27 PM   #15
moonzie
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Quote:
Originally Posted by Hawk296 View Post
Sounds like it's an engine calibration thing. either something in the fueling or maybe an open loop/ closed loop transition or something like that.
I thought closed loop was just when the engine was warmed up? Why would the ECU switch to an entirely different set of tables (open) during WOT?

P.S. doing some research I stumbled upon this thread. Had me cracking up! Absolutely amazing.....

Last edited by moonzie; 01-21-2009 at 09:18 PM.
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Old 01-22-2009, 10:59 AM   #16
BajaSleeper
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I even had the hesitation on my AT. Its tuning that creates the hesitation. I bought the Dastek Piggback Unichip for my car and ever since, I no longer have the hesitation. I'm pretty sure if you get it tuned, it will solve your problem even if you have a 5MT.

As soon as I plugged that baby in and turned on my car, took it around the neighborhood, I could feel a huge difference. Maybe worth considering?
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Old 01-22-2009, 11:41 AM   #17
deadlydave
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Quote:
Originally Posted by BajaSleeper View Post
As soon as I plugged that baby in and turned on my car, took it around the neighborhood, I could feel a huge difference. Maybe worth considering?
Even though we're kinda getting away from the thread topic, I totally agree with this. It really woke up the car, and yielded better gas mileage. Easily chopped at least a tenth off my 0-60 time.
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Old 01-22-2009, 01:34 PM   #18
Eskimo1
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Brilliant! I love modifications with the excuse that's it's to fix something!

Did some searching on the Unichip and didn't read much positive about it, but I suppose even a canned tune would work, since the car is bone-stock.

Better MPG would be a big plus, as she's not too happy with the low 20's we're getting, but there are lots of hills around where we live.
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Old 01-22-2009, 01:47 PM   #19
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Quote:
Originally Posted by Eskimo1 View Post
Brilliant! I love modifications with the excuse that's it's to fix something!

Did some searching on the Unichip and didn't read much positive about it, but I suppose even a canned tune would work, since the car is bone-stock.

Better MPG would be a big plus, as she's not too happy with the low 20's we're getting, but there are lots of hills around where we live.
AP is available for our cars, since the baja ecu hasn't been broken yet. So UniChip would be a great way to go. The thing about it is, it can be customly tuned which is awesome. You just have to find a UniChip certified tuner around you. Theres like 4 of them here in Wa. Definitely the first thing I noticed when I took it around the block was the hesistation was gone.
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Old 01-22-2009, 02:17 PM   #20
Eskimo1
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So the Baja ECU can't be re-flashed like the Sti's, and Legacy's?

And umm.. AP?
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Old 01-22-2009, 03:48 PM   #21
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AP = Access Port Just another way to tune a car.

Not sure about reflashing or anything.

The Dastek Piggback Unichip is PnP. You should read up about it. I know it comes with a reset switch on it.

http://xcceleration.com/dastek.htm
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Old 01-22-2009, 04:25 PM   #22
deadlydave
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Quote:
Originally Posted by BajaSleeper View Post
AP = Access Port Just another way to tune a car.

Not sure about reflashing or anything.

The Dastek Piggback Unichip is PnP. You should read up about it. I know it comes with a reset switch on it.

http://xcceleration.com/dastek.htm
I don't know about the Autos, but the manual ECU is tunable. I got my stage 1 last year, and i'm on a '1.5' adjusted tune, will be stage 2 in the spring when I can get to a dyno. Open-Source is awesome.
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Old 01-22-2009, 11:35 PM   #23
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deadlydave
Is Dom doing your tune? If so,I would like to compare your map to mine. I have a 555 opensource tune.
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Old 01-22-2009, 11:36 PM   #24
moonzie
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Some ECUs for the Bajas have been cracked and can be modified using freely available open source software - just requires a cable. And then that takes us into a whole new thread's worth of discussion and what you would need to tune, how to tune, etc..

Myself, I don't know much about how to tune, so aside from a base entry level map that I purchased from a fellow ex-nasioc member online for $100. More power, but I'm positive it could use some fine-tuning - but that's something I don't feel comfy enough to dig into on my own on my daily driver.
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Old 01-23-2009, 12:16 PM   #25
deadlydave
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Quote:
Originally Posted by moonzie View Post
...Myself, I don't know much about how to tune, so aside from a base entry level map that I purchased from a fellow ex-nasioc member online for $100. More power, but I'm positive it could use some fine-tuning - but that's something I don't feel comfy enough to dig into on my own on my daily driver.
This is the blessing and the curse of open-source. Cobb and others off the shelf tunes are 'safe', but each car's engine is unique. The custom tune gives one the perfect tune for their car, but it might not be so hot on another car, even the next one off the assembly line.

Oh yea, and you can totally nuke your engine if you don't know WTF is up, that's why I don't have a tactrix.
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