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Old 05-17-2009, 05:31 PM   #1
SethV
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Member#: 121995
Join Date: Aug 2006
Default car runs horrible with maf plugged in but fine when not

Like it says I have a 2004 sti and the car ran fin all of a sudden after putting stock tgvs in and 2 trips the car started acting up it woud start fine and after about 20 seconds the idle dips down and the car has no throttle responce starts sputtiering and pinging and will shut off on its own after a few more seconsds

But if I unplug the maf the car runs completly smooth. I tried to use a friend maf off another 04 sti and did the same thing.

I have 1 cel for tgv having low input due to me cutting the wires on accident installing the tgvs butt conected them just to plug the sensor in.

Thanks.
Seth.
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Old 05-17-2009, 05:44 PM   #2
MartinSTi05
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Location: Rockford, Il
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2006 wrx STi

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Sounds like you have a post maf leak.
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Old 05-17-2009, 07:48 PM   #3
dexterous
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Location: Slippery Rock, PA
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2005 STI - Insanity!
2014 WRX - Daily

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You need to either borrow or build a pressure tester and find the leak. Do a search and find some picts. I think I spent about $25 on the one that I built and got all the parts from Home Depot. One word of advice, do NOT overpressure your motor. In my opinion, the system should only see about 10psi with the motor not running so that you dont blow out your oil seals.
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Old 05-17-2009, 08:14 PM   #4
bcblues
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May also be a bad MAF sensor.
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Old 05-17-2009, 10:18 PM   #5
ThreeEleven
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2007 WRB WRX
EJ257

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Could a very dirty maf sensor cause this also? I don't know. It was just an idea.
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Old 06-12-2009, 06:06 AM   #6
05wrx09
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2005 WRX

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Bump for followup.

Did you ever find the culprit? Just curious because although I'm not experiencing your idle issue and I haven't tried removing the MAF altogether, I'm told I might have a Post-MAF leak because of my AF #s or whatever. They're way too high usually, so I forget if that means I'm running lean or rich, I forget. Anyways, I've tried the DIY boost leak tester and couldn't find any leaks. I had my oil cap off though...
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Old 06-12-2009, 10:35 AM   #7
the suicidal eggroll
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It's a dirty or dead MAF or a leak after the MAF
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Old 06-14-2009, 05:43 PM   #8
JasonOJordan
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Im having the same issue how ever my car runs/idles fine up to 5500 rpm then it gets kinda a sputtering noise and it is very had 2 get past that point and it seems to have no power. I unpluged my maf and obviously had no power but it eaisly moved past the 5500 rpm mark with no notable change in engine noise. i had the maf sensor out about 2 weeks ago and cleaned it because when i got the car the filter that was on there was so pluged even after washing it for almost a half an hr you could still not see through it. when i pulled my maf sensor it was very much caked in dirt. After cleaning it fixed another issue but not this one is it possible because of the amount of dirt it is faulty? or would you suspect a leak somewhere?

Also just a side note i also have stock tgv's and am getting a circuit 2 low

Last edited by JasonOJordan; 06-14-2009 at 05:46 PM. Reason: forgot usefull info
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Old 06-14-2009, 06:09 PM   #9
Longarm
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'11 WRX Hatch
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Quote:
Originally Posted by MartinSTi05 View Post
Sounds like you have a post maf leak.
+1+2+3+4+5+6+7+8+9 - car ran fine prior to install, accid. cut wires while install of stock part. Did you reset ecu ? the car will run fine with leak if you disconnect maf, so if it runs fine it sounds to me like a leak.. good luck
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Old 06-14-2009, 06:29 PM   #10
Got Boost?
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hopefully you did not over tighten the manifold to the tgv housings as they require very little torque...8inch/lbs if I remember right. My dealer hooked me up and did this when I broke a ring land, a cracked tgv housing is what I got for no extra charge

It has to be a leak after the maf as mentioned, especially since you tried a known good maf in your car and got the same result. also, you might wanna check the turbo inlet, as you were just working around it.
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Old 06-15-2009, 12:46 AM   #11
JasonOJordan
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where are some common leak areas that would cause a high rpm sputter that is no longer there with the maf unplugged?
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Old 06-15-2009, 10:42 AM   #12
the suicidal eggroll
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a tear in the turbo inlet
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Old 06-15-2009, 04:19 PM   #13
JasonOJordan
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mine had one awhile back but i fixed it. Also im fairly certain that its the MAF sensor causing the issue as my CEL came on today maf sensor circut low.
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Old 06-15-2009, 09:21 PM   #14
bcblues
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Blue w/ custom bug splat

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Almost certainly a MAF sensor or a post MAF leak.
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