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Old 03-06-2013, 08:29 AM   #1
vrcoupe
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Default 05 wrx pulsating help

I have an 05 wrx and when you are on it it starts pulsating and jumps between 15-20 psi boost. I don't know much about the car but it has an intake, bigger top mount intercooler, hks bov, and 3in turbo back exhaust with no cat. If someone could give me an idea what might be wrong that would be great. I was thinking it might need injectors??
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Old 03-06-2013, 09:41 AM   #2
JMSok8
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I got a crap tune once that made the car have a back and forth feeling in the higher gears and the boost would fluctuate just as you are describing. It wasnt a violent feeling, but trying to accelerate on the freeway sucked. I would do some data logs and report back.
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Old 03-06-2013, 10:23 AM   #3
Dakota D
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my suggestion is to check for leaks,also bovs if leaky can cause this issue a crap intake could also cause issues if its not tuned for.
what intake is on it?
do you know if its tuned?

Last edited by Dakota D; 03-06-2013 at 10:33 AM. Reason: spelling
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Old 03-06-2013, 10:39 AM   #4
vrcoupe
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Quote:
Originally Posted by Dakota D View Post
my suggestion is to check for leaks,also bovs if leaky can cause this issue a crap intake could also cause issues if its not tuned for.
what intake is on it?
do you know if its tuned?
I don't know if it has a tune or not and it has some cheap intake on it.
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Old 03-06-2013, 11:01 AM   #5
Dakota D
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cheap as in ebay cheap? that could be the problem right there(maf readings could be severly skewed) and if its not tuned thats a double wammy,that can cause alot of other issues.

when it pulsates does the car feel like its jerking?
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Old 03-06-2013, 11:40 AM   #6
vrcoupe
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Quote:
Originally Posted by Dakota D View Post
cheap as in ebay cheap? that could be the problem right there(maf readings could be severly skewed) and if its not tuned thats a double wammy,that can cause alot of other issues.

when it pulsates does the car feel like its jerking?
Ok, it's not jerking its like a smooth pulsating.
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Old 03-06-2013, 11:44 AM   #7
Dakota D
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hmm.have you checked for leaks yet like i suggested earlier?
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Old 03-06-2013, 11:48 AM   #8
vrcoupe
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Quote:
Originally Posted by Dakota D View Post
hmm.have you checked for leaks yet like i suggested earlier?
Not yet I'm going to be doing that later today.
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Old 03-07-2013, 01:59 PM   #9
blubug_768
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I just read about this, its apparently common w/stock bcs. The remidy would be 3 port ebcs + tune.
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Old 03-07-2013, 02:35 PM   #10
vrcoupe
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Would the turbo going bad cause this?
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Old 03-07-2013, 02:45 PM   #11
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Check the vacuum line that goes from the turbo to the T-fitting before the stock BCS. There should be a small "restrictor pill" in the line somewhere that controls the amount of flow from the turbo to the sensor so it can accurately read boost levels. Make sure the machines hole in the pill doesn't have something blocking the consistent flow.


http://www.clubwrx.net/forums/tuning...-data-log.html

Go to post 10 there's a diagram.
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Old 03-08-2013, 04:53 PM   #12
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Quote:
Originally Posted by vrcoupe View Post
I don't know if it has a tune or not and it has some cheap intake on it.
Usually such intakes flow more than stock airbox, around 20% more in closed loop/off-boost, and between 0-10% in open loop, resulting in engine running lean and all it takes is one good knock and engine goes BOOM.

Quote:
Originally Posted by Dakota D View Post
hmm.have you checked for leaks yet like i suggested earlier?
It's good to check for holes/slits in the bcs vacuum lines, if there is one that means that air is bleeding, without ECU's knowledge, without bcs/ebcs ever getting chance to bleed/intercept that air, this results in less pressure being applied against wastegate, resulting in higher boost, you overshoot the target boost, turbo dynamics kicks in, you undershoot, and you keep oscillating back and forth.

Quote:
Originally Posted by blubug_768 View Post
I just read about this, its apparently common w/stock bcs. The remidy would be 3 port ebcs + tune.
Not really a common problem, if you're unlucky you're bcs seizes to work, which in turn it doesn't bleed any air, so all that pressure coming from compressor outlet gets applied against wastegate, once you hit 7/8psi, clapper opens up and you won't run anymore boost than that.

Quote:
Originally Posted by vrcoupe View Post
Would the turbo going bad cause this?
No.
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Old 03-09-2013, 12:58 AM   #13
ogboot
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If the boost is oscillating you are overshooting your boost target. Best fix is to look up how to adjust your wastegate arm.
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