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Help with Learning View


DoDo1975

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Recently had new shortblock and head rebuild on my 05 LGT

 

Unfortunately the idle is a little rough.

 

I ordered a cable and pulled the learning view but am having trouble interpreting it.

 

From what I have read, it seems to be running fairly rich due to the negative numbers.

 

What might this mean, especially considering it is worst in the mid ranges?

 

Thanks

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i would first visually look at all the vacuum lines and bigger connections. the main two spots people have problems with is the connection between the intercooler and the throttlebody and there is a vacuum line T under the intercooler that comes off every once and awhile. after that if you cant find anything obvious then do a test. you can do a google search for that. you can buy a kit or make one. i made one out of metal just because thats the easiest for me but lot of people make them out of pvc/abs.
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take the intake S tube off, attach unit there. build to 5-6 psi, listen for leaks, you'll hear your evap valve buzz but it will go away on it's own. typically a loss of 1 psi per second is acceptable, anything quicker is not. you'll hear air rushing out while you fill it if you have a decent leak
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i would first visually look at all the vacuum lines and bigger connections. the main two spots people have problems with is the connection between the intercooler and the throttlebody and there is a vacuum line T under the intercooler that comes off every once and awhile. after that if you cant find anything obvious then do a test. you can do a google search for that. you can buy a kit or make one. i made one out of metal just because thats the easiest for me but lot of people make them out of pvc/abs.

 

That damn t under my TMIC came off the other day too... took me a while to find it too. I stuck a ziptie around it, better not fall off again

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take the intake S tube off, attach unit there. build to 5-6 psi, listen for leaks, you'll hear your evap valve buzz but it will go away on it's own. typically a loss of 1 psi per second is acceptable, anything quicker is not. you'll hear air rushing out while you fill it if you have a decent leak

 

I never hear anyone mention the three lines attached to the turbo inlet tube when hooking up a tester like this. i plug or pinch off these vacuum/vent lines. if you don't you will lose a ton of air into your crankcase. i would also test it a couple psi over what your car is running at. make sure you take your oil filler cap off also.

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the reason you keep them connected and pressurize to a lower pressure is because those lines could be the cause of the vac leak. keep the cap on but don't pressure more than 6psi or so. the cap off- of course the air will escape through the pcv and out the filler hole.
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Well after removing the intercooler and looking for loose or disconnected vacuum lines, I noticed the duct coming off the turbo looked mash.

 

I am assuming this is whats referred to as a ripped turbo inlet?? This must have happened when my short block and turbo was replaced in October. I have included picture, there would definately be air getting in.

 

So, would this cause rough idling? I assume it would constitute a boost leak?

 

What can I do about it? Can I seal it with some type of spray goop or do I need to replace it ASAP? If so, any idea how long this would take? Are there risks to driving it

 

Is this the shops fault, or should I have specified to replace this tube? (I supplied the parts)

 

Thanks

ATT59323.thumb.jpg.61cd8a9ce315fab0cbf4782785e30cad.jpg

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That piece could be the cause of your issues. It is kind of the shops fault and kind of not. That gets old and brittle because of that, it's very easy to tear when reinstalling the turbo. They may not have noticed that they did that. That having been said, it should have been replaced one way or another.
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the reason you keep them connected and pressurize to a lower pressure is because those lines could be the cause of the vac leak. keep the cap on but don't pressure more than 6psi or so. the cap off- of course the air will escape through the pcv and out the filler hole.

 

well when i look for a boost leak on mine i pressurize to 22psi so thats why i do it the other way.

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Well after removing the intercooler and looking for loose or disconnected vacuum lines, I noticed the duct coming off the turbo looked mash.

 

I am assuming this is whats referred to as a ripped turbo inlet?? This must have happened when my short block and turbo was replaced in October. I have included picture, there would definately be air getting in.

 

So, would this cause rough idling? I assume it would constitute a boost leak?

 

What can I do about it? Can I seal it with some type of spray goop or do I need to replace it ASAP? If so, any idea how long this would take? Are there risks to driving it

 

Is this the shops fault, or should I have specified to replace this tube? (I supplied the parts)

 

Thanks

 

that is a vac leak, yes. 05-06 inlet tubes are notorious for being thin and tearing easily. best bet is to replace it, simply changing out turbos can be all it takes for it to tear.

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  • 2 months later...

I replaced this tube about 1 month back. (2005 Subaru Legacy GT)

 

My fuel trims still look the same with 5-12% negative values, and I still get stumbling at idle as well as poor fuel economy (10-15% worse than it should be).

 

From what I have read, it is likely 1 of 3 things.

 

MAF sensor

Vacuum Leak (Boost)

Front Left Oxygen Sensor

Dirty Throttle plate?

 

What should I test first? Is a smoke test something easy to do to test for Vacuum Leak? Anything else I can do to narrow it down? Is there a good how to on vacuum lines so I know I can find them all?

 

If the roughness occurs immediately on startup, does this mean it is happening in open loop and rule out the MAF and O2 sensor?

 

Thanks

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  • 3 weeks later...

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