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Stumble at cruise only


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I inspected it when I was swapping turbos. It was mooshey but didn't find any leaks.

 

I will check it again by using a smoke machine and slight pressure soon.

 

I would think if I had a post MAF/pre turbo leak my fuel trims would show the ecu adding fuel to compensate or there would be other signs when data logging.......but will still check it.

10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned.

 

SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC.

Best 0-60: 4.651 by AP

1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission.

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My saga continues. Basically everything I have checked on the car, checks out. Not an oxygen sensor issue, all the parameters are within the norm, car drives fine, acts fine, rock solid cruise, hits target boost quick, etc etc. Absolutely no symptoms of an issue except that cruise stutters.

 

 

I see you have a 2005, have you replaced the black o-rings between the intake manifold and the TGV's with the new larger orange ones ?

 

Also are you sure your TGV's are working correclty ?

 

There is also some talk of a longer fuel hose from the FPR to the engine that may help surging/stutters.

 

http://legacygt.com/forums/showthread.php/fuel-line-mod-220064.html

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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I see you have a 2005, have you replaced the black o-rings between the intake manifold and the TGV's with the new larger orange ones ?

 

Also are you sure your TGV's are working correclty ?

 

There is also some talk of a longer fuel hose from the FPR to the engine that may help surging/stutters.

 

http://legacygt.com/forums/showthread.php/fuel-line-mod-220064.html

I have TGV deletes (because they failed, heh), they have also been ported/polished. At that time new gaskets were put in and the car ran fine.

I would expect to see an air leak of any sort to show up in logs, no?

I will definitely struggle to look at my turbo inlet, but again, this stumble should be there at all times and/or register somehow on readings.

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Correct.

 

I'm just throwing out ideas, for all who read this and have the same issue. Could be a combination of small things...?

 

Thinking about it, my wagon has a little stumble in the summer time. Now that its cold out I don't notice it.

 

I'll be doing the fuel line mod in the spring.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Looks like my oxygen sensor is the culprit. This is what I posted in my other thread.

 

I monitored A/F Correction and it's all over the place.

When I hold the pedal steady it will oscillate between 0 and +-6%

As soon as I engage cruise, it will spike to anywhere between -25% to + 18%. Within a fraction of a second it would go from deep negative into deep positive.

I have never logged AF Correction but I take it this is not normal?

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I have pulled all 4 coils again, bent each pin a little to make better contact to the connector.

 

I have also installed a fuel pressure gauge which effectively extends the fuel line a few inches.

 

I'll post back in a few days with any improvements or no change.

10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned.

 

SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC.

Best 0-60: 4.651 by AP

1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission.

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and dont figure on an inlet/post maf problem showing up in logs as ecu fuel correction. since it is unmetered air getting in after the maf the ecu sees all as normal and doesnt add additional fuel to compensate for the air it doesnt read. if that makes sense.

 

and if that inlet was "mooshy" i would look into replacing it, once stock inlets get like that due to oil impregnation of the rubber you are looking at a possible collapse and turbo suffocation every time the boost comes on.

 

these problems dont show at all times because of boost most likely. it seems that everyone having these issues is having them at the same rpm (around 3k) which is the average area during normal acceleration for our cars to cross over into boost phase, thats why im suggesting the inlet. but anything specifically correlated to the onset of additional suction/pressure due to higher boost levels is where i would focus all attention.

 

and as far as o2 sensors bouncing from + to - that is normal. it compensates back and forth at a rapid rate as each cylinder fires and changes the readings. if youve ever looked at one of the cheap a/f gauges (non wideband) youll see the needle constantly sweeping back and forth.

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jeffy2.5xt, Point taken but a question regarding it not showing on logs.

 

Wouldn't the ecu start adding to the fuel trims based off the o2 readings since it thinks xxx air is entering the intake but o2 is saying lean, so ecu add more fuel? Or do these ecu's not do that?

10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned.

 

SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC.

Best 0-60: 4.651 by AP

1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission.

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a little of both fish.

 

and yes these cars, as most do, will adjust accordingly depending on the readings from the o2. but they have an "acceptable" level. hence the reason people get knock and blow their motors up before they even knew what hit them. this is not to say that these are concrete facts, just suggestions.

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I'm unsure which part # to use to order the O2 sensor now ... I found 22641aa32a on the boards here but can't confirm if that's still current or what. If I look it online I can find it on Fred Beans Parts for little over $130, however if I do a long search for year/make/model, it comes up with a sensor for $119, both OEM.

Local dealer wants $190, wouldn't give out part # of course.

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I logged this AM. After the car warmed up while in cruise. No funny o2 readings. Pretty stable between 0-6% correction. Sometimes a spike to 8.

 

Then I duplicated the stumble. No flux in 02. So this appears to be a multiple cause problem. As mine is not the o2s.

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I'm unsure which part # to use to order the O2 sensor now ... I found 22641aa32a on the boards here but can't confirm if that's still current or what. If I look it online I can find it on Fred Beans Parts for little over $130, however if I do a long search for year/make/model, it comes up with a sensor for $119, both OEM.

Local dealer wants $190, wouldn't give out part # of course.

 

 

So did you call the guy's at FB's ? I would at least call and talk with them to make sure you get the right one.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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I ordered my front o2 at amazon. Was the exact oem style.

Denso 234-9120

 

[ame=http://www.amazon.com/Denso-234-9120-Oxygen-Sensor-Ratio/dp/B001F799X6/ref=au_as_r?ie=UTF8&Make=Subaru|13&Model=Legacy|64&Year=2006|2006&carId=001&n=15684181&newCar=1&s=automotive&vehicleType=automotive]Amazon.com: Denso 234-9120 Oxygen Sensor (Air and Fuel Ratio Sensor): Automotive[/ame]

10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned.

 

SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC.

Best 0-60: 4.651 by AP

1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission.

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Keep us updated over the years and let us know if it last.

 

If it fails I'll post it on here.

 

I don't see why Denso would fail early. They make great quality sensors.

10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned.

 

SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC.

Best 0-60: 4.651 by AP

1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission.

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