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Old 06-03-2010, 12:29 PM   #1
Daluv
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Join Date: Sep 2007
Default 06 STI VACUUM Hesitation

Hi,

I am unable to pinpoint where is the problem. So usefull help is welcome

Car: 2006 STI 48000km
Mods: Catted DP + Maddad Exhaust + K&N Air filter + PROTUNE

Symptoms: Since STOCK, around 2000-3000 RPM in VACCUM ( around -10PSI ) with a CONSTANT pedal input, the car is hesitating. You can see the RPM going up and down and that car bucking while cruising. This behavior is gear and speed independant but it is worse at low speed evidently.
It runs A1 with medium pedal input or at WOT.


Software:

I have the same behavior with the PROTUNE MAP, the cobb stage 2 map, XPT stage 2 map and the stock map. It is less present on the stock map but it is enough to be annoying.

IAM = 1

Hardware:

PCV Valve: Replaced it. No change.

MAF: Inspected and cleaned. Voltage have been monitored with Romraider. No change. Ran without the MAF. No effect.

Crankshaft sensor: Inspected anc clean. No change.

Fuel Pump/ Fuel filter: NOW CHANGED 2010.04.03 - NO CHANGE.

Fuel Pressure regulator vaccuum hose/line: Not checked

Front 02 sensor: Changed 2 weeks ago. No effects.

Grounds: Have checked the easiest one.

Transmission ground: Need to be checked.

Sparks plugs: 50% life remaining. Oil on the threads of #2 and #4...

Coilpack: Visually Inspected OK

Motor Mount: Change for GroupN. NO CHANGE

Pitch Stop: Change for a Torque Solution. NO CHANGE.

Header: Stock to Maddad lately. No change.

Pressure test: There was no leaks.

Idle is fine.

I drove my friend 07 that has been protuned at the same time as mine and it doesnt hesitate and feel great to drive. I even consistently put down more power than the 07 on the dyno.


I even played with the DBW tables. I changed the Requested Torque table. Made it smoother like the 07 STI table and the hesitation was still present.

Is there something I overlooked or i should consider beside selling the damm car?

Some logs:

https://spreadsheets.google.com/ccc?...5QWh2RGc&hl=en

https://spreadsheets.google.com/ccc?...KWE80MFE&hl=en


thanx

Mart
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Old 06-03-2010, 01:22 PM   #2
ktmrider
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2005 Legacy GT - 6MT
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Two things that the LGT folks have found in your situation:

1. OCV or AVCS solenoid being a bit sticky
2. Rear O2 sensor bad or slow response

Most have found one of the OCV's bad, search "OCV" for more info on how to log the duty cycle(s).
The rear O2 sensor was less common altho from what I have gathered in addition to monitoring cat efficiency it also has input on AFR's at cruising speeds ( which does fall into your problem category ).
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Old 06-03-2010, 01:43 PM   #3
Daluv
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I will try to log the following:

<parameter id="P50" name="Intake OCV Duty Right" desc="" ecubyteindex="14" ecubit="5">
<address>0x00003E</address>
<conversions>
<conversion units="%" expr="x*100/255" format="0.00" />
</conversions>
</parameter>
<parameter id="P51" name="Intake OCV Duty Left" desc="" ecubyteindex="14" ecubit="4">
<address>0x00003F</address>
<conversions>
<conversion units="%" expr="x*100/255" format="0.00" />
</conversions>
</parameter>


The fix for bad ocv is removing the filter in the banjo bolt? Change valve?

Mart

Quote:
Originally Posted by ktmrider View Post
Two things that the LGT folks have found in your situation:

1. OCV or AVCS solenoid being a bit sticky
2. Rear O2 sensor bad or slow response

Most have found one of the OCV's bad, search "OCV" for more info on how to log the duty cycle(s).
The rear O2 sensor was less common altho from what I have gathered in addition to monitoring cat efficiency it also has input on AFR's at cruising speeds ( which does fall into your problem category ).
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Old 06-03-2010, 01:47 PM   #4
ktmrider
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^^ Yep those are the parameters. You will log them at idle and at 2500rpm or so and watch the change.
Removing the banjo filter is definitely one way to fix the issue, some will also say to just clean it so there is still some protection for the turbo ( RH side feeds both AVCS and turbo ).
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Old 06-03-2010, 01:53 PM   #5
Daluv
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I removed my screen from the banjo of the turbo oil supply line 2 weeks ago and it was clean...

OK I will look into those values and report back.

thanx

Mart

Quote:
Originally Posted by ktmrider View Post
^^ Yep those are the parameters. You will log them at idle and at 2500rpm or so and watch the change.
Removing the banjo filter is definitely one way to fix the issue, some will also say to just clean it so there is still some protection for the turbo ( RH side feeds both AVCS and turbo ).
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Old 06-03-2010, 02:17 PM   #6
Daluv
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as described here:

http://www.scoobymods.com/tsb-02-97-...82.html?t=5782

?

Quote:
Originally Posted by ktmrider View Post
^^ Yep those are the parameters. You will log them at idle and at 2500rpm or so and watch the change.
Removing the banjo filter is definitely one way to fix the issue, some will also say to just clean it so there is still some protection for the turbo ( RH side feeds both AVCS and turbo ).
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Old 06-03-2010, 04:15 PM   #7
ktmrider
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Yep, another link http://legacygt.com/forums/showthrea...light=ocv+duty starting at post #10.
OCV duty at idle should be around 10% with no AVCS advance. Once you get the RPM's around 2500 the AVCS should start advancing, if not then the OCV solenoid is bad.
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Old 06-04-2010, 01:20 PM   #8
Daluv
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Old 06-05-2010, 11:51 AM   #9
ktmrider
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^^ Those look good for the 2000+rpm range, what are they doing at idle?
Idle should have OCV around 10% and AVCS advance at 0.
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Old 06-05-2010, 01:03 PM   #10
Daluv
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both OCV Duty are sitting at 9.41 and AVCS is at 0 degrees per spec

Mart

Quote:
Originally Posted by ktmrider View Post
^^ Those look good for the 2000+rpm range, what are they doing at idle?
Idle should have OCV around 10% and AVCS advance at 0.
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Old 06-05-2010, 02:46 PM   #11
ktmrider
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2005 Legacy GT - 6MT
Black

Default

Yep, all looks good with the AVCS.
Try the rear O2 sensor from your friends car, may sound weird but it has fixed a few LGT's with that.
Also inspect the inlet tube carefully, not sure if you changed yours but many develop tears at the turbo from the clamp.
Hope you figure it out!
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Old 06-05-2010, 04:42 PM   #12
Daluv
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Default

I change my FPR which is under the inlet so I replaced it (grimmspeed) and everything is really tight.

I wonder if I can run without a rear 02. I am running right now without a Front 02 but it doesnt do any changes to my hesitation.

I will research more to see where in the ECU code does the rear 02 is used as an input. I always thought it was only for the cat to make sure it was working correctly.

thanx

Mart

Quote:
Originally Posted by ktmrider View Post
Yep, all looks good with the AVCS.
Try the rear O2 sensor from your friends car, may sound weird but it has fixed a few LGT's with that.
Also inspect the inlet tube carefully, not sure if you changed yours but many develop tears at the turbo from the clamp.
Hope you figure it out!
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Old 07-07-2010, 08:55 AM   #13
Daluv
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so taking a look at the shop manual in engine diagnostic on the subject of the rear oxygen sensor:




check idle?




so let's go for a SLOW ride and log the same exact data as the Engine diagnostics page.





so uhm let's try this again because I am stupid and clueless..




I unplugged the rear 02 to do a small test and went for a ride... almost all hesitation seems to be gone now.... let's see what the dealer will do...

thanx to ktmrider for the tip.

Quote:
Originally Posted by Daluv View Post
I change my FPR which is under the inlet so I replaced it (grimmspeed) and everything is really tight.

I wonder if I can run without a rear 02. I am running right now without a Front 02 but it doesnt do any changes to my hesitation.

I will research more to see where in the ECU code does the rear 02 is used as an input. I always thought it was only for the cat to make sure it was working correctly.



Mart
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Old 08-11-2010, 10:13 AM   #14
Mike2000GT
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Location: Media, PA
Vehicle:
2006 WRX Wagon
SGM

Question

Updates?

My car has nearly 60k on it and I'm getting the hesitation during cruise.

I think I'll try the rear O2 swap.

Thanks
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Old 08-11-2010, 10:23 AM   #15
Daluv
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Default

I had the rear 02 sensor changed on warranty and the stuttering is still present with the new rear 02

we did some logging with the SSM at the dealer and the graph were pretty much the same with the new one

Mart

Quote:
Originally Posted by Mike2000GT View Post
Updates?

My car has nearly 60k on it and I'm getting the hesitation during cruise.

I think I'll try the rear O2 swap.

Thanks
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Old 09-09-2010, 12:59 PM   #16
Mike2000GT
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Just an update on my hesitation. I had the clutch fork squeak really bad (where the fork resonates on its pivot while the clutch pedal is out). I fixed the squeak with some moly lube this past weekend, and magically the hesitation during cruise is gone too!

My theory is that the clutch squeak was bad enough that it was triggering the knock sensor. Other than the fix the car, route, and weather conditions were nearly identical pre and post fix.

HTH
Mike
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Old 09-09-2010, 01:01 PM   #17
Daluv
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did you record knock while logging or it is a theory?

Quote:
Originally Posted by Mike2000GT View Post
My theory is that the clutch squeak was bad enough that it was triggering the knock sensor.
HTH
Mike
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