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Old 09-13-2010, 03:05 AM   #151
guilty_619
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hmm... keeping an eye on this thread. i have a 4eat wrx stage 2, mods include: invidia up-pipe, invidia 3" down-pipe, spt exhaust and spt intake with heat shield.
my car started to hesitate right after i got my stage 2 tune, just after i pulled out of the shop actually. didn't think anything of it at first, but then it started to occur more often (haven't contacted tuner about the problem). it only seems to hesitate in 3rd gear at 3,000-3,250. the rpm fluctuates rapidly between said rpm's for about a second or two, maybe longer, depending on how much throttle i put down. basically, the faster i accelerate, the less amount of hesitation i have. if i start from a stop and go full throttle, then switches into 3rd gear at higher rpm than normal, it doesn't hesitate at all. very weird.
if its in 3rd gear, under normal driving conditions (not going over 75% throttle) chances are it will happen. hopefully you guys can understand what i'm talking about, i kinda have a reputation for not explaining very well
if i remember anything else, i'll be sure to post. been thinking of posting a video of it, if that will give people some ideas.
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Old 09-13-2010, 07:41 AM   #152
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Quote:
Originally Posted by Phatron View Post
I tried various throttle mappings and I believe another tuner did also.

There could be a loose/bad ground somewhere causing voltage fluctuations to the ecu or through the pedal angle sensor wires.

Mart have u done a compression check? I just inspected a car and it had a lopey idle and hesitation and one of the cylinders was completely dead, compression was 0.
well what i was really getting at isnt the map itself but a small spot in throttle position where throttle voltage doesnt change or is incorrect. basically tps not reading correctly for throttle angle. i think no matter how much you play with your maps you would never tune it out. dont know if this has been ruled out but older outbacks are common for bad tps, but i dont think you can replace tps with DBW you have to replace whole TB assembly.
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Old 09-13-2010, 07:59 AM   #153
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is there a diagram that shows all the grounding points? i have a meter and ive cleaned the grounds that i could see and the one on the firewall.my hesitation seems to get worse when im low on fuel. it was doing it bad yesterday with quater tank. what about the avs like mentioned above?

again my idle is perfect and it starts right up
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Old 09-13-2010, 08:48 AM   #154
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nope, no compression test done. I guess it will be the next step.

The car under boost is as fast as any stage 2 STI... so compression should be good I guess...

Mart

Quote:
Originally Posted by Phatron View Post
I tried various throttle

mappings and I believe another tuner did also.

There could be a loose/bad ground somewhere causing voltage fluctuations to the ecu or through the pedal angle sensor wires.

Mart have u done a compression check? I just inspected a car and it had a lopey idle and hesitation and one of the cylinders was completely dead, compression was 0.
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Old 09-13-2010, 10:28 AM   #155
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My partner was running 12.0's in his vf Sti with a cylinder that had cracked rings that was below 100 psi.
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Old 09-13-2010, 10:30 AM   #156
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Ok, was it hesitating?

Mart

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Originally Posted by Phatron View Post
My partner was running 12.0's in his vf Sti with a cylinder that had cracked rings that was below 100 psi.
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Old 09-13-2010, 12:32 PM   #157
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my point was that the cars can run fine and make power with cracked rings.....in response to you saying "but it still makes power, so its probably not the rings"
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Old 09-13-2010, 12:37 PM   #158
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understood.

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my point was that the cars can run fine and make power with cracked rings.....in response to you saying "but it still makes power, so its probably not the rings"
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Old 09-13-2010, 07:58 PM   #159
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man, i hope thats not the case. thats some money right there to have the motor rebuilt.
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Old 09-13-2010, 08:35 PM   #160
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i really doubt thats it as its been happening since 2500 miles off the lot...

try going through and cleaning all your grounds, subaru likes to ground on top of the paint, just take em off and sand off the paint
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Old 09-13-2010, 09:32 PM   #161
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ive cleaned them already. most of them thread in .they should be getting good contact maybe not on the surface but the bolt should. im thinking its something tune based since between all of us we've pretty much changed all the parts that could have to do with fuel delivery. there's a bunch of threads on the forester forum about this issue.
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Old 09-13-2010, 10:07 PM   #162
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Try using this spreadsheet....many people have reported it to stop their hesitation

http://www.romraider.com/forum/viewt...hp?f=32&t=5483
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Old 09-18-2010, 03:33 AM   #163
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bump guys, 04 sti here, 95k miles. it's been hesitating for the last 4-5k miles. Tried everything the OP has, and still no fix. I agree with the consensus of it being a mechanical issue. My compression test was fine, and i'm still hesitating. I think it's an intake leak or a failing sensor. I will try to have someone log some data for me soon and post it up.
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Old 09-20-2010, 04:20 PM   #164
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Quote:
Originally Posted by Snakebot View Post
I have a different DBW throttle body that I'm about to try.
Just an update since I last posted.

I pulled the intake manifold/TGV and replaced all of the vacuum lines and gaskets with new ones. I also installed the spare (used) DBW throttle body that I had. I didn't replace any sensors.

The hesitation's still there. It doesn't consistently happen now. For example it didn't do it this morning but I noticed it a couple of times yesterday.

I guess the next step is to start replacing sensors one by one. Any suggestions on which one I should start with?
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Old 09-20-2010, 04:22 PM   #165
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Have you pressured tested the intake for leaks after everything was back on? If not, I would make sure I can hold pressure before doing anything else.

Mart

Quote:
Originally Posted by Snakebot View Post
Just an update since I last posted.

I pulled the intake manifold/TGV and replaced all of the vacuum lines and gaskets with new ones. I also installed the spare (used) DBW throttle body that I had. I didn't replace any sensors.

The hesitation's still there. It doesn't consistently happen now. For example it didn't do it this morning but I noticed it a couple of times yesterday.

I guess the next step is to start replacing sensors one by one. Any suggestions on which one I should start with?
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Old 09-20-2010, 07:42 PM   #166
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possibly a smoke test? i'm going to try and have one done on my car. If you're unfamiliar with it, it's where smoke is injected into your intake. It will come out where ever there is a leak in your intake system.
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Old 09-20-2010, 07:57 PM   #167
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even better but you still need to pressurized the system. A standard evap leak tester does not have enough pressure alone.

Quote:
Originally Posted by hatched91 View Post
possibly a smoke test? i'm going to try and have one done on my car. If you're unfamiliar with it, it's where smoke is injected into your intake. It will come out where ever there is a leak in your intake system.

Last edited by Daluv; 09-20-2010 at 08:20 PM.
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Old 09-20-2010, 09:13 PM   #168
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true. don't just hook up pressure to your turbo inlet and go to town. there is a specific procedure so you don't blow out seals/grommets, etc. It's like 5psi for the inlet, and then only like 20max for intercooler to the heads. There are some things you have to remove, so be sure to read up on it BEFORE trying it lol
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Old 09-21-2010, 12:42 PM   #169
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Quote:
Originally Posted by Daluv View Post
Have you pressured tested the intake for leaks after everything was back on? If not, I would make sure I can hold pressure before doing anything else.
Wouldn't the symptoms be different if the post tubo intake track wasn't holding pressure? Like not being able to hit boost targets? I haven't noticed a problem with hitting peak boost.

Maybe my logic is flawed but it seems to me that if there was a leak in the intake tract, the symptom would occur across a wider RPM range.

The hesitation I'm experiencing only occurs between 2500-3000 RPM, during throttle tip-in on light throttle application (> 10%) and off boost (boost gauge shows vacuum). There's no problem at other RPMs under the same conditions.

I've had a compression test done about 6 months ago and the results were normal. The idle vacuum is normal when checked at the brake booster port.

The problem has existed with two different motors, the stock motor and the current built (RAW Performance) motor. Three tunes, OTS AP, Opensource and AP ProTune.
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Old 09-21-2010, 12:46 PM   #170
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My hesitation ALWAYS occurs pass -9.8PSI (vacuum)... light throttle... yours?

Quote:
Originally Posted by Snakebot View Post
Wouldn't the symptoms be different if the post tubo intake track wasn't holding pressure? Like not being able to hit boost targets? I haven't noticed a problem with hitting peak boost.

Maybe my logic is flawed but it seems to me that if there was a leak in the intake tract, the symptom would occur across a wider RPM range.

The hesitation I'm experiencing only occurs between 2500-3000 RPM, during throttle tip-in on light throttle application (> 10%) and off boost (boost gauge shows vacuum). There's no problem at other RPMs under the same conditions.

I've had a compression test done about 6 months ago and the results were normal. The idle vacuum is normal when checked at the brake booster port.

The problem has existed with two different motors, the stock motor and the current built (RAW Performance) motor. Three tunes, OTS AP, Opensource and AP ProTune.
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Old 09-22-2010, 01:54 PM   #171
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Quote:
Originally Posted by Daluv View Post
My hesitation ALWAYS occurs pass -9.8PSI (vacuum)... light throttle... yours?
Yup, I'm experiencing the hesitation at approx. the same vacuum level.

I can reproduce the problem pretty consistently by cruising at 2500 RPM in 3rd gear and slowly rolling in on the throttle and keeping the throttle opening low (~<5%). The car will hesitate, it feels like the ECU is pulling timing. The hesitation is gone by 3000 RPM.

However, I've only noticed the hesitation once or twice since I replaced the all of the vacuum hoses and manifold gaskets.
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Old 09-22-2010, 02:01 PM   #172
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Will all you guys please try this sheet and see if it works

http://www.romraider.com/forum/viewt...hp?f=32&t=5483
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Old 09-22-2010, 02:38 PM   #173
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I tried but it feels like it has "move" the hesitation or changed the way it occurs. I asked if it was an iterative process in the thread... maybe you need multiple iteration to dial it in perfectly.

Quote:
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Will all you guys please try this sheet and see if it works

http://www.romraider.com/forum/viewt...hp?f=32&t=5483
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Old 09-29-2010, 01:50 AM   #174
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hello guys i have a 06 sti and having the same issue for the last two days around 10psi vacum 2500-3000 rpm crusing and accelerating cant figure out the issue either
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Old 09-29-2010, 08:24 AM   #175
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Mileage? Mods? What have been done to try the cure the issue?

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Originally Posted by acjdmb18 View Post
hello guys i have a 06 sti and having the same issue for the last two days around 10psi vacum 2500-3000 rpm crusing and accelerating cant figure out the issue either
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