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Discussion Starter #1
what if you were to detach the vacuum line to the FPR & drive the car this way for a while? what would happen? how would it affect performance? my friend has a 90lx & he had his vacuum removed for some time. he bought his car & had it for about a year before he decided to install an AFPR wich is when he noticed the line missing off the top. he had a fuel pressure guage underhood & saw it read 38 psi often at idle when he looked under there not realizing it should only read this way with the line disconnected. we followed my vacuum line on my stang to see where it came from & put a new one on his in the same mannor. his line was totally gone altogether! he asked me how this affected his car and did he hurt anything but i wasnt sure of the answer, so i need help answering this one for him.
thanx!
 

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Discussion Starter #2
anyone know? why have the vacuum line connected to the FPR?
 

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well I am not really sure why it is there but with it gone that means he had a vacuumn leak which was definly hurting performance of the car. I don't believe there is any long term damage from doign this, the car probably just ran really bad while it was gone.
 

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car would think it was at WOT all the time and run rich...

eventual carbon on compustion chambers and possible cat failure... but he's probably ok...
 

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Discussion Starter #5
so it thinks its running WOT all the time? i'm glad i asked, i thought it would only hurt idle..........
thanx!
 

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Without the vaccuum line attached, there is no "regulator" in the "fuel pressure regulator". It's not that it thinks it's running full throttle all the time, it's just that line pressure is now unregulated so that at any given injector pulsewidth it's dumping more fuel in it than it needs to. The O2 sensors will read this extra fuel and attempt to narrow down the pulsewidth, probably unsuccessfully, but what will happen when he plugs the FPR back in without clearing the computer's adaptive memory is he'll run WAY lean until the computer adapts.
 

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Discussion Starter #7
thanx for the info!
 

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I take that back...I can't remember if disconnecting the vacuum increases or decreases fuel pressure. It might decrease it in which case the computer is trying to richen it and when he fixes it it'll run rich. Either way it'll mess up the mixture.
 

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Discussion Starter #9
disconnecting the line increases pressure.........can anyone figure out why somone would totally disconnect the FPR vacuum line? would there be some benefit to this? mabey somone wanted to run rich allowing for more timing & possibly N2O w/o the worry of detonation!? the car feels exactly the same before & after the line was reattached, even the idle stayed the same. car reacted the same from idle to 5k in 4 gears..............
any response would be appreciated!
 
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