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imdabes
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937 Posts
Discussion Starter #1
Having issues finding this answer via search.

96 xlt 5.8

I put a KN filter on awhile back and ditched the filter box as I fabbed up an aluminum box for it. I initially planned on fabbing the entire exhaust, and cut the crank breather tube off the y adapter that comes off the throttle body and stuck a small filter on it.

About 20 or 30 miles later the engine threw a lean bank 1 and 2 code. I cleared it and it kept coming back.

Engine isn't affected much, feels a little sluggish but I also just put 200lbs worth of dynamat and other soundproofing in :D

I remember reading at some point introducing unfiltered air into the system throws codes, but shouldn't the computer re-learn that its not getting crap dumped out of the crankcase back into the intake? That breather hose gets to the intake after the MAF sensor, so I don't know how that could be the cause of the code.

Do I need to go grab a new y pipe thing with the breather tube intact or is there something else I can do?


Also, my exhaust rusted off at the y pipe so my o2 sensors are actually basically in fresh air, I wondered if that tripped the code but I don't really know, its been like that for awhile now.
 

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aka: kemicalburns
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7,842 Posts
the o2 sensors being exposed to fresh air are more likely your issue. regardless that should be fixed first.
 

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Registered
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141 Posts
Any air entering the intake after the MAF will register as un metered air and cause issues. The system doesn't care if the air is clean or dirty, it only knows that the air/fuel ratio is off.
 

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4,869 Posts
The PCV line in the air intake system is taking filtered air OUT of the intake tubing, into and through the engine, and then out of the engine and into the intake manifold by virtue of the manifold vacuum.
If you have air going INTO the intake side, you either have something screwed up, or you have more blowby that the PCV system can handle.
 

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imdabes
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937 Posts
Discussion Starter #5
Intake side of the breather is sealed, crankcase side has a small filter.

Sounds like its the exhaust, I'll order my headers asap and get her to the shop
 

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Roller rockers are gay
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19,197 Posts
This is an intake issue. put it back to the way the factory had it and the codes will go away. Your setup is allowing unmetered air into the engine AFTER the maf sensor, that's why it's throwing lean codes.

The computer doesn't "relearn" this, that goes against it's entire logic. It thinks there's something wrong, and that's because there IS. It runs fine because it's dumping fuel in to account for the extra air. It can only do so much to compensate before it throws a code and says "Fix me!" That's why it's sluggish, a 5000lb bronco doesn't give 2 f*cks about an extra 200lbs of soundproofing.

Besides, it's been long debated and generally agreed that a drop in K&N, with the factory cold airbox and insulating the intake tubes is the best way to make the intake tube as efficient as possible. You're driving around with a vacuum leak and it's telling you it's not happy.
 

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imdabes
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937 Posts
Discussion Starter #8
Got it, so running a line from the crank case to the new filter would accomplish the same thing then right? I can't find that stupid y tube adapter anywhere
 

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imdabes
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937 Posts
Discussion Starter #10
The only thing in the intake that is changed is that y pipe that has the crank breather on it.

I'll just figure some way to re-attach that hose. I'm sure a barb will work fine
 

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aka: kemicalburns
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7,842 Posts
probably time to post up some pictures
 
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