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Old 12-07-2005, 01:16 AM   #1
Helium
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Member#: 102393
Join Date: Dec 2005
Default Boost creep and Spiking STOCK!!! Help!

Ok, how can I be getting this?

WOT 4th gear from 50mph, causes my boost to spike past .1 to .13 - .14 or so (~3 ticks) then it will "wave" at me between .1 and .06 very fast, about 1/2 second down and 1/2 sec up, as I feel the car surge and slack.

This started happening recently after my last fill up, and with the 11 degree weather.

1,2,3rd gears are all fine under WOT, they go just past .1 (As I would expect in cold weather), but If I am in 4th, 5, 6 and hit the gas just enough to get max boost pressure, (Independent of throttle position) I will still get the same "Wave" as I do in WOT.

What is happening?
Is it normal for extreme cold?
Can it be fixed?
Do I have bad gas this time and the ECU is retarding timing to prevent knock in the cold?
Did I miss something?

This is scary, as I have no mods...
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Old 12-07-2005, 08:16 AM   #2
96Lconversion
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2008 Infiniti G35S
2005 S2000

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As you have no mods, I would assume that you got some bad gas, or maybe you put a lower octane in by accident? Subarus are very sensitive to gas. I'm assuming you have an STi because you said 4th, 5th or 6th gears, but what year is it? Best advice would be to take it to the dealer and take a mechanic for a ride and reproduce the problem for him.
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Old 12-07-2005, 08:17 AM   #3
2fas4u
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Chapter/Region: MAIC
Location: Manchester, Maryland
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2005 STI / 2009 STI
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Are you running an STI? The VF39's are common to that problem. I think the cold makes it worse in some. Usually you see this with the common mods, TBE, Catless DP, etc...
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Old 12-07-2005, 12:17 PM   #4
Helium
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Default It's an STI

I was guessing bad gas because the pumps were making some weird noises. At 1/4 tank, I filled it back to full with 93 + octane booster. Will see if that makes a difference today.
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Old 12-07-2005, 12:22 PM   #5
96Lconversion
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Quote:
Originally Posted by Helium
I was guessing bad gas because the pumps were making some weird noises. At 1/4 tank, I filled it back to full with 93 + octane booster. Will see if that makes a difference today.

Yeah, I'd be interested to know if that fixes it.
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Old 12-07-2005, 01:22 PM   #6
bboy
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I doubt it's your gas. It's either a boost control system problem or you have true boost creep (wastegate port problem).
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Old 12-07-2005, 02:29 PM   #7
Helium
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Default 93 + Octane boost no effect

I think the car has a more serious issue, prob with the boost controller as it's boosting over 20psi. On stock setup, that's probably not a good thing... I will have to check into it further, and let you guys know what I find.

A cool side effect is incredibly fast spool between 0 and .07 though.. It's like freereving your engine to 5k.. that fast, but then comes the retardation as I think the ecu is detecting something and is taking precautionary steps to keep boost from jumping too high.
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