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Discussion Starter #1 (Edited)
I have a weird problem. It has only developed recently. My car only hit fuel cut in low gears and only when i go Wide open throttle.



Say if i'm at second gear and decided to hit pedal to the metal (WOT), the car will boost so fast to 15psi that i'll hit fuel cut within seconds.

BUT...

if i gradually boost it up to 15psi, i'll never see fuel cut.... ??!?



WTF is going on?


I ruled out vaccum leaks because my vaccum is reading 21-22 psi at idle.

Before...i can hit 18psi without having any problem. This situation just developed recently.
 

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A Happy Dad
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that happens to me when my mix it too rich, as a matter of fact I can richen just by one or two points and it will do it, lean it out just until it doesn't..... I do assume that you've ruled out a small boost leak
 

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Discussion Starter #3
mdr40z said:
that happens to me when my mix it too rich, as a matter of fact I can richen just by one or two points and it will do it, lean it out just until it doesn't..... I do assume that you've ruled out a small boost leak
What's the difference between a boost leak & a vaccum leak in symptoms wise? Are they 2 completely different thing?
 

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Kroze said:
What's the difference between a boost leak & a vaccum leak in symptoms wise? Are they 2 completely different thing?
vaccum is not postive manifold pressure (psi) it doesnt blow off intercooler pipes. Vaccum is created by the motor pulling in the air it needs to make a combustion stroke. You may have awesome vaccum but you can still have a major boost leak. Your turbo makes the postive manifold pressure, thats why theres two sides of the guage.

On top of that are you for sure its fuel cut. When your car fuel cuts it will feel like a brick wall for a split second, your CEL will come on and then the ignition will kick back in and keep trying to run. Its very violent.
 

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Discussion Starter #5
z1turbo said:
vaccum is not postive manifold pressure (psi) it doesnt blow off intercooler pipes. Vaccum is created by the motor pulling in the air it needs to make a combustion stroke. You may have awesome vaccum but you can still have a major boost leak. Your turbo makes the postive manifold pressure, thats why theres two sides of the guage.

On top of that are you for sure its fuel cut. When your car fuel cuts it will feel like a brick wall for a split second, your CEL will come on and then the ignition will kick back in and keep trying to run. Its very violent.
yes i'm very sure it's fuel cut :-/

i've run over 12psi on stock turbo & afm before and i think i've experience fuel cut more than anyone.


Check engine light came on, car just feel like it hit something and then it continues driving as normal. but if i keep on holding the gas down, it'll just keep on doing as if i repeatedly hitting a brick wall.
 

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Just some guy
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Vacuum is mostly casued by the engine sucking against the restriction of the throttle body. So a vacuum leak that affects the manifold vacuum is usually located after the tb (manifold/runner gaskets etc). There's also a few vacuum lines running from the manifold and things like the egr that may cause it.

A boost leak would be anything losing air after the turbo, which include all of the IC pipes, bov, etc, along with anything that would ALSO cause a vacuum leak (manifold gaskets etc). More stuff to check out when looking for a boost leak.
 

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Discussion Starter #7
Racefiend said:
Vacuum is mostly casued by the engine sucking against the restriction of the throttle body. So a vacuum leak that affects the manifold vacuum is usually located after the tb (manifold/runner gaskets etc). There's also a few vacuum lines running from the manifold and things like the egr that may cause it.

A boost leak would be anything losing air after the turbo, which include all of the IC pipes, bov, etc, along with anything that would ALSO cause a vacuum leak (manifold gaskets etc). More stuff to check out when looking for a boost leak.
So the problems that i'm experiencing is pretty much caused by boost leak. And that either caused by Intercooler & Pipes & Gaskets on the manifold?
 

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Just some guy
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^^Yup. Basically check anything that carries air or seals against anything that carries air. But since you say you have 21 in/hg of vacuum, all the manifold stuff *should* be ok, so I'd start with the IC and IC pipes.
 

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I've never been able to boost past 16 psi without hitting fuel cut at high rpms without taking out some of the AF signal with my SAFC
 

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mdr40z said:
that happens to me when my mix it too rich, as a matter of fact I can richen just by one or two points and it will do it, lean it out just until it doesn't..... I do assume that you've ruled out a small boost leak
Happens to me too due running rich on high boost, but never gave me a check engine light.
Also be very carefull when you lean ur mixture, may kill ur engine.
 

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Discussion Starter #11
Doh, found out today i have 2 codes.

34 - which is normal when you have fuel cut right?
51 - which is also normal because i took the TPS out the other day and readjust it.
 
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