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Old 09-03-2010, 12:32 PM   #126
Daluv
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I bought the car around 22000km and noticed it a little while after... it was BONE stock and hesitating a bit.

Mart

Quote:
Originally Posted by Snakebot View Post
I have been fighting the the same hesitation on my '04 STi for over three years now.

For me, changing the fuel pump didn't resolve the problem.

Just out of curiosity, approx. how many miles did you have on the car when you first noticed the hesitation?
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Last edited by Daluv; 09-03-2010 at 12:45 PM.
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Old 09-03-2010, 02:40 PM   #127
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My neighbor just had his intank fuel fuel split in half.
It was hesitating before but I tuned around it not really thinking much of it until the filter just assploded.
The hesitation was rampant when it split as it was just spewing half the fuel back into the fuel tank....basically just a loss of fuel pressure.
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Old 09-03-2010, 03:30 PM   #128
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I change the fuel pump and the fiter and it hasnt changed the hesitation at all so I dunno

I am redoing the BPV gasket as we speak..

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Originally Posted by Phatron View Post
My neighbor just had his intank fuel fuel split in half.
It was hesitating before but I tuned around it not really thinking much of it until the filter just assploded.
The hesitation was rampant when it split as it was just spewing half the fuel back into the fuel tank....basically just a loss of fuel pressure.
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Old 09-03-2010, 04:17 PM   #129
Daluv
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also does the purge valve helper side front of the intake can be source of problem? I noticed on the 2011 sti engine that port is capped on the intake strangely...

dealer is asking 40$CAD @#$#@$
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Old 09-03-2010, 04:19 PM   #130
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Quote:
Originally Posted by Daluv View Post
I bought the car around 22000km and noticed it a little while after... it was BONE stock and hesitating a bit.

Mart
Based on that I would take it to the dealership and tell em to keep it till it's fixed or to work out a trade in. Seems like there is just something inherently wrong in your motor.
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Old 09-03-2010, 04:20 PM   #131
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Quote:
Originally Posted by Daluv View Post
I change the fuel pump and the fiter and it hasnt changed the hesitation at all so I dunno

I am redoing the BPV gasket as we speak..
You said you have a Forge 100% recirc BPV 2010.08.30. Is it possible that it doesnt shut fully until it sees boost?
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Old 09-03-2010, 04:24 PM   #132
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That was the first thing I have done, 5 visits 3 dealership. Master tech said "it is normal" "we dont see anything anormal with the SSM" bla bla.. we dont have the lemon law here and dealership are incompetent, I can tell you that. Every dealership I went to (4 in total).

that's why I started developing my own SSM tools and stuff to figure it out... I am quite sure the sampling rate is not high enough at 4800bps to help pinpoint the problem. I wish I had time to redo what freon did to change the baud rate in the ECU I have on my bench with my rom.

Even Ben@ecutek cant figure it out heh.

Mart

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Originally Posted by Phatron View Post
Based on that I would take it to the dealership and tell em to keep it till it's fixed or to work out a trade in. Seems like there is just something inherently wrong in your motor.
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Old 09-03-2010, 04:25 PM   #133
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Stock or FORGE BPV, the car hesitation is almost identical...

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You said you have a Forge 100% recirc BPV 2010.08.30. Is it possible that it doesnt shut fully until it sees boost?
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Old 09-03-2010, 05:43 PM   #134
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i wish i could ride along with you to feel the hesitation. Its so strange how its prominent enough for you to feel, yet you cant get anything strange to show up in your logs.
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Old 09-03-2010, 06:02 PM   #135
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I think what mart just said about it happening in stock form pretty much narrows it down to an inherent mechanical problem somewhere.

We've changed everything....boost, timing, fueling, avcs, pedal feel, etc.....and nothing got rid of it.
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Old 09-03-2010, 07:34 PM   #136
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so is your car dumping fuel to and running rich? i hope i didnt waste money on a o2 . it could be ecu. mine was doing it when i was stock, i have 85,000 miles on it. is your exhaust popping when you revv it?
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Old 09-04-2010, 06:31 PM   #137
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Quote:
Originally Posted by spec_bg View Post
so is your car dumping fuel to and running rich? i hope i didnt waste money on a o2 . it could be ecu. mine was doing it when i was stock, i have 85,000 miles on it. is your exhaust popping when you revv it?
Mine started hesitating around ~78K miles. The last log I had did show it running rich when the hesitation occurs. There's no popping when I rev the motor.

I agree with Phatron, it's something mechanical. I've had the same hesitation with two different long blocks and turbos. It's not the tune since I get the hesitation with the stock, open source, OTS AP and ProTune maps.

So far I've ruled out the front O2 sensor, the MAF, fuel pump/filter, coil packs, TGVs and FPR. I have a different DBW throttle body that I'm about to try. If that doesn't solve it, I'm thinking of replacing the knock sensor.
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Old 09-04-2010, 10:19 PM   #138
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so are you guys ruling out anything tuning wise? if its mechanical sounds like it would take forever to pinpoint a cause for!
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Old 09-05-2010, 09:21 AM   #139
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im catlesss so that could be why its popping.but the tip of my muffler has a lil condensation on it at idle and blackish,so its def running rich. when you say mechanical are you talking engine internals?
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Old 09-05-2010, 03:09 PM   #140
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Originally Posted by spec_bg View Post
im catlesss so that could be why its popping.but the tip of my muffler has a lil condensation on it at idle and blackish,so its def running rich. when you say mechanical are you talking engine internals?
mechanical meaning something that cant be tuned out. ie. if you have a misfire you cant tune it out.
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Old 09-06-2010, 09:31 AM   #141
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what are the odds of the ecu being bad? it looks like we're narrowing it down though. if i unplugg the o2 and the cel comes on will it go off when i plug it back in. im about to try this.
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Old 09-06-2010, 10:02 AM   #142
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what are the odds of the ecu being bad?
well I was told by a US tech that his dealership has changed some 06 STI ecu regarding the hesitation issue. I dont understand how the ecu can be at fault in that case... I have one sitting on my bench...

Quote:
Originally Posted by spec_bg View Post
it looks like we're narrowing it down though. if i unplugg the o2 and the cel comes on will it go off when i plug it back in. im about to try this.
it will go off after a little while but will stay in the memorized bank.

Mart
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Old 09-09-2010, 08:28 PM   #143
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well, i just installed the new o2 and took it out for a drive ,i also reset ecu. it still has the same issues with the pulsing acceleration. im thinking its ecu at this point. im stomp after reading all these threads with people with the same issues. some fix it and some dont.
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Old 09-09-2010, 11:40 PM   #144
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i dont even want to know how much a new oem ecu would cost!
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Old 09-09-2010, 11:48 PM   #145
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Only like $300 iirc
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Old 09-12-2010, 11:01 AM   #146
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any updates? my xt was doing it bad on the way to work yesterday. when you step one the gas to go into boost or pass a car it seems to hiccup for a quick sec and then accelerate.
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Old 09-12-2010, 11:02 AM   #147
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no update but I have a new map revision to try out from phatron as soon as I fix my new leak...
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Old 09-12-2010, 10:43 PM   #148
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I had the Same problem with my 04 STi, The problem ended up being cracked ring lands. My AVCS would jump around from 2500 - 3000 RPMs after that it would be fine. Even WOT from a very slow roll there would be no hesitation but just partial throttle it would act up. Not saying this is your problem but just from my experiences with Subaru Blocks the cylinders are not perfectly round; they have a slight oval to them from the factory. At least the last 4 blocks that I have bought and My Block that was Stock in my04 STi.
All I can say is good luck and hope its not cracked ringlands like mine
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Old 09-13-2010, 12:57 AM   #149
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no update but I have a new map revision to try out from phatron as soon as I fix my new leak...
Have you tried logging your throttle body position while slowly pressing down on the pedal. see if the tps voltage is smooth. i have never seen a problem on DBW throttle body but i have seen driveablity problems from bad tps on other subys.
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Old 09-13-2010, 02:24 AM   #150
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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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