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Old 04-28-2002, 11:15 AM   #1
DragII
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Default 2.5rs Stalling after turbo install

what should we look for first? All vac lines seem tight, and non restrictive, also there is no cel code thrown.

car is a 99 2.5rs with t3/t4 turbo kit.
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Old 04-28-2002, 12:17 PM   #2
hayscoob
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Maybe a failing MAF sensor? Fuel cut of some sort? Kinked vac tube? Good luck, I hope you find out what it is...

Paul...
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Old 04-28-2002, 01:03 PM   #3
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How does it stall, I mean can you drive it at all? Or does it stall right away?
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Old 04-28-2002, 01:07 PM   #4
DragII
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It stalls both when shifting to neutral, and coasting to a stop, or at idle after reving to 3k or higher.
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Old 04-28-2002, 01:10 PM   #5
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Had the same problem...I'm told its attributed to high fuel pressure....you probably have High flow fuel pump and maybe RRFPR too?
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Old 04-28-2002, 01:20 PM   #6
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sounds like fuel pressure..what size injecotrs are you using BTW?
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Old 04-28-2002, 02:07 PM   #7
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yeah we are running stock injectors
holly intank high flow pump 255lph
Vortech FMU 4:1

fuel pressure is prolly pretty high, we've tried leaning it out on the s-afc...it helped a little, but still has the same problem after 4k rpm.

thanks for all the quick replies
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Old 04-28-2002, 02:14 PM   #8
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I had a friend whos car alwasy died just like yours does. His was because his was because of 2 reasons. Either because he was super rich when he went to Neutral cause his Blow off valve was vented to atmosphere and 2 because his Cartech RRFPR was messed up.

Brad
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Old 04-28-2002, 02:22 PM   #9
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BOV does vent to open air. although it's 2 completely differant cars, that never caused a problem w/ my turbo honda.

Is that a common prob for Impreza's?
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Old 04-28-2002, 02:26 PM   #10
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fair warning that the subaru stock ECU for a 2.5 sucks (in my opinion) the honda stock ecu can do ok with AFI but subarus is a diffrent beast all togeather. I would suggest looking into knock protection, parrell fuel rails and bigger injecotrs to protect yourself from engine detonation...
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Old 04-28-2002, 02:43 PM   #11
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Quote:
Originally posted by STiTuner
Either because he was super rich when he went to Neutral cause his Blow off valve was vented to atmosphere....
Ding ding ding! This is the reason. Your BOV is venting to atm. and letting air out that the MAF had already accounted for, causing the ECU to throw lots of fuel in there and run rich as hell. There used to be something that the S-AFC users used to do to lean out mixture during shifts, but I don't remember exactly what.
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Old 04-28-2002, 02:54 PM   #12
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Quote:
Originally posted by DragII
BOV does vent to open air. although it's 2 completely differant cars, that never caused a problem w/ my turbo honda.

Is that a common prob for Impreza's?
The Honda has a MAP sensor so it doesn't decide how much fuel you need until after it's through the throttle body. If your 99 has a MAF, which I'm pretty sure it does, it wieghs the air before going through the turbo so it thinks you have a LOT more air than you actually do. You'll need to reroute the BOV to your intake between the MAF and the Turbo. That should fix it.

Chad
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Old 04-28-2002, 06:08 PM   #13
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If you have an AFC fish out the manuel. The Instruction Manuel one. Look on page 22 for setting the "Dec. Air Correction"
Honestly I can't really make 100% sense out of what it says in there. If you don't have the manuel (or there is enough demand) I'll type out the page.
Good luck
Mike
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Old 04-28-2002, 07:05 PM   #14
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I agree with 8,

Vent the BOV to atmosphere with a MAP equipped car is not a problem, however, with the MAF equiped cars, the BOV has to be vented back upstream of the turbo and downstream of the MAF.

If you do this, it should solve the problem.
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Old 04-28-2002, 08:47 PM   #15
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ahhhh that makes sense....thanks alot guys...we'll give that a shot!

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Old 04-29-2002, 11:53 AM   #16
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Does the car bog when you are at 50% throttle above 4k? Do you get backfiring a lot and the smell of fuel when sitting idle? If you are you are just running way to rich and need to adjust the fule pressure.

Is the Vortech FMU 4:1 located after your stock FPR? You need to get rid of that stock FPR. That will not flow well with the bigger pump and you fuel pressure at idle I woudl expect to be around 50 PSI with it. So with the Vortech and the car's ECU you car is probably running as high as 65 PSI. How muhc boost are you running, iof you are running only 5 pounds then you are running to much fuel.

Stock at idle under vacuum is 34 psi. As for the AFC I don't think you can adjust the fuel enough with that stock FPR in the line. You will want to get an adjustable FPR. Then the AFC will work better for smaller amounts of tuning.

So you are probably just running way to rich. I never had a problem with the BOV location and I also have a 99RS. Mine vent's to open air and is after the Turbo, located on the IC. And it does not sound like a broken MAF. Though you car could be setup differently somehow. Maybe you should check for air leaks between the Turbo and the intake manifold also.

just my $0.02
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Old 04-29-2002, 11:58 AM   #17
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havent' had any bogging, and the boost is at 5psi.
bov is on the intercooler. it does smell a little rich.
So you never had the problem with the BOV venting to open air?
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Old 04-29-2002, 11:59 AM   #18
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Quote:
Originally posted by markus
I agree with 8,

Vent the BOV to atmosphere with a MAP equipped car is not a problem, however, with the MAF equiped cars, the BOV has to be vented back upstream of the turbo and downstream of the MAF.

If you do this, it should solve the problem.

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Old 04-29-2002, 06:13 PM   #19
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Let's try to clear this up a little...

Quote:
It stalls both when shifting to neutral, and coasting to a stop, or at idle after reving to 3k or higher.
So you are saying that the car stalls when you are not under boost? Basically you are just coming to a stop or sitting idle but you never hit boost? So therefore your BOV will not let air escape to atmosphere, correct? It is as if you have an NA car, correct? If this is the case I would say you just need to drop your idle fuel pressure. Which you should probably get an adjustable FPR to lower your fuel pressure. Does the car hunt a little at idle?

Now if the stalling occurs after you have boosted and let off the gas then it is probably to much fuel running in because of the MAF sensor reading more air then there is. I will agree with everyone else on that statement. But if the idle fuel pressure is set correctly this should not make that much of a difference, should it? Can anyone confirm this with me, just wondering how much air is actually escaping and wether you really need the AFC to correct for the loss of air?

So if you vent downstream of the MAF and upstream of the Turbo couldn't you cause back pressure for the air going through the MAF, possibly sending air the wrong way, possibly damaging the MAF? Think of it this way and correct me if I am wrong. If you are under boost, mass quantities of air are getting drawn through the MAF, then all of a sudden you let off on the throttle. So now there is no boost and all kinds of pressure build in the IC. So now your BOV will vent 5 pounds of pressure between the Turbo and the MAF. Of course it can't go back to where it came from so it will want to escape past the MAF.

If anything letting the BOV vent to atmosphere has helped to drop the number of pings I get between hard shifts, especially with 280cc's. So letting air escape between hard shifts is it a good or a bad thing?

Just trying to clear this up...

Last edited by skywalker; 04-29-2002 at 06:23 PM.
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Old 04-29-2002, 08:29 PM   #20
DragII
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yeah it's happening even when not coming out of boost. Most BOV vent a little bit of air even when not under boost. it's not a lot..but a significant amount, I thought that is what you guys were refering to....Not being familiar with MAF sensors...that kinda made some sense..but I am starting to think this is infact more of a fuel pressure problem....

So, dropping fuel pressure at idle I think will be the next step.
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Old 04-29-2002, 09:18 PM   #21
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I posted this in another thread that was talking about high baseline fuel pressure. Yesterday I started my car at my friends house, and about three seconds after, the car stalled. It had never done this before, and proceeded to do it a second time after I started it. Now I began to worry, though I did recognize that my fuel pressure was just unusually higher than normal. I started the car a third time and boom, up she went, just like normal.

I talked to edekker here on the board and he said one day just to mess around he cranked his fuel pressure up bit by bit until the car would die. He said his car finally stalled out at 56 psi of fuel pressure.

My fuel pressure is roughly around 50-51 psi at idle, so it is a very good possibility this is why my car stalled out, as I mentioned the the FP was just slightly higher than normal.


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Old 04-29-2002, 11:53 PM   #22
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Would you guys recommend an SVX fpr, or an aftermarket one?

thanks again for all the replies, and ideas!
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Old 04-30-2002, 12:08 AM   #23
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The SVX is a good solution from what most people are saying. Another possibility is an aftermarket one. On Summit racing look for a SX Performance Regulator.

Here si the part number: AEI-13109
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Old 04-30-2002, 11:56 AM   #24
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Sorry subachad, didn't even see your post
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Old 04-30-2002, 02:22 PM   #25
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it's all good, I was just a little surprised.

Chad
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