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Old 09-23-2013, 06:32 PM   #1
dakyn
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Default Bad boost fluctuation

Hey guys how's it going.

I've got a 2003 wrx and I just put the Cobb 3" turboback exhaust on a few weeks ago. Before I put the exhaust on I was getting a tiny bit of boost creep(I think that's what it's called). It would over boost to about 13.5 then come back to 10 and stay there, which is where it usually is. After I put the exhaust on it got a little worse, over boosting to 15, dropping to 7, then going back to 10. The other night I noticed that the boost is starting to fluctuate really bad. Mostly happens in 4th and 5th gear at wot and in 2nd and 3rd if I'm at 3k rpm and then go wot. It will over boost to 15, drop to 7, then bounce between 7 and 13 all the way to redline. Yesterday the car started to not go above 5 psi in 1st gear.

I've looked at all my hoses and they are all fine as far as I can see. I took it to a mechanic and they blamed it on my gauge, but I disagree because I can feel the boost going up and down. I haven't been able to get a firm answer from anyone, but so far the things that have been suggested are the wastegate, the bpv, or maybe a tune.

I plan to get the car tuned soon on a dyno but I wanted to make sure I fixed this problem first. I will be getting a new digital boost gauge soon so I can make sure that it's not the gauge, but again I don't think that's the problem.

The only mods on the car is the turboback and a drop in filter

Any help would be greatly appreciated, so far I haven't been able to figure anything out, even from my Subaru mechanic.

Thanks!
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Old 09-23-2013, 07:18 PM   #2
sultanofsubguns
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It probably went into limp mode since you aren't tuned and the ecu is trying to save the motor.
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Old 09-23-2013, 07:26 PM   #3
96SubyImpreza
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Quote:
Originally Posted by sultanofsubguns View Post
It probably went into limp mode since you aren't tuned and the ecu is trying to save the motor.
He doesn't need a tune on a 2003 WRX.

It could be something as simple as the wastegate actuator or an issue with the boost control solenoid. Has the car ever had any modifications before you purchased it?
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Old 09-23-2013, 07:34 PM   #4
dakyn
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Stock when I bought it. Why wouldn't the 2003 need a tune?
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Old 09-23-2013, 10:23 PM   #5
DZXN
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2004+ cars have a leaner factory tune and the switch from closed to open loop fueling can have you running lean enough to do bad things. 02-03 are not as environmentally friendly, but can stay somewhat with mods before a tune. Only from stock to stage 2 though, it's not like you can throw random turbos and injectors at it.
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Old 09-23-2013, 10:49 PM   #6
paulpat
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Looks like you have everything covered. How about hose clamps on the vacuum tubes and then check the ebcs. Something about hooking it up to a battery.... honestly the tune will probably smooth it out
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Old 09-27-2013, 01:03 PM   #7
dakyn
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Getting it tuned this weekend, if that doesn't work I'm going to try to adjust the wastegate and check the ebcs.

Thanks guys!
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Old 09-27-2013, 03:09 PM   #8
danger1138
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Forget about getting a digital boost gauge, thats the least of your problems. I would look into getting a wideband and an AFR gauge, much more important IMO.

Also seems like the mechanic isnt much help at all blaming the issue on the gauge. Its not a matter of just watching the gauge and reading the boost values fluctuate, u would actually feel it. I mean to go from 15psi then drop to 7psi then swing back up to 10psi... U do feel it dont your or are you just reading the gauge?
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Old 09-27-2013, 03:53 PM   #9
RockRex
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Smoke test for leaks. I "looked" for leaks on mine and it looked fine. Smoke test revealed hole in inlet.
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Old 09-27-2013, 04:52 PM   #10
IA Performance
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If you need a tune and need a boost gauge then why not pick up an AccessPORT? It comes with Off The Shelf maps (OTS) specific to stage 2 modifications. You could even find a used one for around $400. Although, for $549 you get a new unit with warranty, which is a nice thing to have with electronics. Think about it if it isn't too late to cancel the dyno tune.

Outside of the accessPORT/Tune I would inspect the waste gate arm to ensure it is able to move freely when pulled open. That is, make sure the arm is not catching on the heat shield and that the flapper door is not being obstructed (highly unlikely since the COBB DP is a bell mouth type).

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Old 10-01-2013, 02:51 PM   #11
dakyn
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Yeah, I can definitely feel the difference in boost, and that's what made me start watching my boost gauge closer. I tried to explain this to the mechanic but they think its all in my head. They never drove my car hard enough/long enough to be able to see it do it.

Tested all the hoses for leaks using soap water and didn't find anything.

I actually had the accessport before the downpipe. I had some troubles with it and it wouldn't flash my car, saying it needs to be initialized. I followed all of the instructions and made sure the initialization cable was plugged in, yet nothing I did would make it work. I called cobb a few times but they only said that It was my cars problem and I would have to buy a new ecu to get it to work. Ended up returning the AP and buying the cobb TBE. Not sure if it really is my car or it was the AP, so the people who are doing the tune are able to fix my car, if there really is a problem, and then tune it. I made a thread about the AP problem but couldnt find any answers. (http://forums.nasioc.com/forums/show....php?t=2528839) A few other people with 2002-2003 wrx's are having the same problem with the AP.

Not sure how to do a smoke test, but it sounds like I should try one.

As for the wastegate, that was the next thing I was going to check and try adjusting it to see what the outcome was.

I posted this issue on another forum and the best answer I got was that it was boost oscillation caused by the wider downpipe and that a tune should fix it. Anyone agree/disagree?
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Old 10-01-2013, 03:49 PM   #12
IA Performance
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Dakyn - if the AP was unable to initialize the ECU then I imagine you may run into another road block when you go to have the car tuned. Be sure to alert your tuner ahead of time too.

Smoke Test = you need to find a shop with a smoke machine.

Wastegate = try lengthening the rod by 1 full turn (counter clock wise). See if that helps.

Stephen
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Old 10-01-2013, 04:08 PM   #13
dakyn
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Yeah, Im going to tell them when I schedule the tune and make sure they have some idea of how to fix it before I go in.

Thanks for the info on the wastegate, I'm going to try it when I get home from work.

PS - I live in Fort Collins, real close to you guys! Hope you're all okay after the flood.
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Old 10-17-2013, 02:18 PM   #14
Luigiwrx
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My car has the same issue, I have an 03 wrx pretty much stock and it seems that when the engine is hot or has been running pretty hard for a nice canyon run then it fluxes more often. But when I pull over and let it cool for about 15-20 mins it boosts regular again but then eventually fluctuates.
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