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Discussion Starter #1 (Edited)
So yesterday I was just studying/admiring the engine bay (as I like to do) and noticed the the vacuum line between the intake manifold and fuel pressure regulator was disconnected from the intake and just sort of dangling there. I am not sure how long it was like that or how it would have happened, but I definitely had been noticing some hesitation, especially under peak boost.
I am wondering what effect this would have had on the engine while it was under boost as well as whether I should be worried about any sort of permanent damage. My current theory goes something like this:

Boosted air would escape from the intake manifold, pushing the A/F toward a rich condition. The fuel pressure regulator will not increase fuel pressure under boost and therefore cause a lean condition and the ECU compensates by raising fuel trim.


Feel free to chime in.​

Edit 9/22/09: here is a pic showing the location of the hose in the engine compartment:
 

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The line coming off would cause the engine to run lean and the ecu may try to compensate, but not enoguh. They reffered to this as the engine killer. Mine actually blew of and it if it wasn't for JMS I would have probably hurt my motor. When i finally connected my wideband I was running mid to hi 13's under WOT. Just reconnect it and put a zip tie on it. Sadly this seems to be a common problem on the X, but easily fixable.
 

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Discussion Starter #3
The line coming off would cause the engine to run lean and the ecu may try to compensate, but not enoguh. They reffered to this as the engine killer. Mine actually blew of and it if it wasn't for JMS I would have probably hurt my motor. When i finally connected my wideband I was running mid to hi 13's under WOT. Just reconnect it and put a zip tie on it. Sadly this seems to be a common problem on the X, but easily fixable.
wow, it popped of on its own? Holy crap, that seems like it could be quite a bad flaw if it really is a common issue. I wondered how mine came off. I had done some work in the engine bay last week, but nothing near that side. Also, the dust on the line (I have a dirty engine bay) was undisturbed, lending further credence to the prospect of the line popping off on its own. It will be receiving a zip tie when I get home.
 

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thats shitty. i might put zip tie round mine just to make sure.
 

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Having that line missing would probably increase your pressure at idle but decrease your pressure @ WOT. Depending on your setup, this could matter a lot or a little.

If you're on a stock tune, you should be safe. I wouldn't sweat it.
 

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Discussion Starter #8

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Just had mine pop off a few days ago, followed by a friend of mine having the same issue the next day. Got a hesitation and lean WB reading. Just installed some super stout hose, and zip ties to prevent this.
 

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Had this happen to me, you should have noticed right away I would think because when mine popped off the car wanted to idle at almost 2k rpm, I was seeing high 13-low 14 afr's at wot with it off on my wideband which I would think would cause damage if you were driving it continually hard or with those afr's. The ecu cannot correct for it nearly enough to keep it in a safe afr.
 

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Discussion Starter #12
Had this happen to me, you should have noticed right away I would think because when mine popped off the car wanted to idle at almost 2k rpm, I was seeing high 13-low 14 afr's at wot with it off on my wideband which I would think would cause damage if you were driving it continually hard or with those afr's. The ecu cannot correct for it nearly enough to keep it in a safe afr.
interesting. my idle was fine and I had just put on a cone filter, so I figured the slight hesitation was due to the afr being thrown off by the filter. I would definitely have noticed a 2k rpm idle..:p
 

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Ahh, glad I found this thread!

Yesterday I noticed my car was starting to hesitate at WOT (especially around 5k RPM), even with my Cobb reflash already. I tried resetting the ECU with no luck.

I checked under the hood and sure enough, the fuel pressure regulator vacuum line was disconnected! :godance:Time for a zip tie!

Thanks!
 

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Same happened to me today. I ziptied both ends. I'm gonna try and see if the oem vacuum line clamps (like the ones that connect to your ebcs with the pill) fit snug. If so, i'll be getting some at the dealer.
 

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I've got 2 questions.

1. What's the range your AFR are suppose to be at, at WOT?
2. What would cause this line to pop off b/c my line is on there real good.
 

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aka Turbo
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im tuned for 11.3-11.5-ish.
high fuel pressure from running richer at WOT under higher boost i'd say
i thought mine were on good too... i found out the quite opposite tonight when i pulled to the light and my car sounded it had cams from idle revving up and down so fast. i then tried to do a pull and the car kept choking upper rpm with no pull
 

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Discussion Starter #18
I've got 2 questions.

2. What would cause this line to pop off b/c my line is on there real good.
Well, I would say it's probably a combination of the rubber in the line losing it elasticity, engine vibration, and boost pressure. Once the rubber starts to break down, it more or less just sits on there less tightly and I'm guessing that it slowly works its way off. Or maybe a good boost spike can do it (since the line is subjected to boost pressure).
 

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Discussion Starter #20
Updated first post with a picture showing the location.
 
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