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fuel lines/fpr and idle issues

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I tried to make this easy to read and easy to follow, but I think it's probably the opposite of that..


I'm a newb with fuel system stuff... legit ocd for a long time, I just don't touch fuel system stuff, kind of like a lot of electrical stuff in my house, with exceptions. trying to figure out what's causing some small issues I'm having with my non-turbo legacy.


Long story short..

-The attached picture is not from my car.

-Does the orientation of these round "dampers" matter? My top one is right side up like in the picture, but the bottom one is sideways, so that the bottom is facing the driver side fender.

-The bottom hose going from the engine to the damper was replaced with napa h175 1/4" fuel line. Could that cause any issues?

-Does the bottom line only take vapors back to the fuel tank or charcoal canister? Or does it carry fuel?

-My car has two of those round "dampers", one on top, one on bottom, just like the picture. I'm guessing one of those is the FPR, but I don't know which one, and why there are two..



Current issues

-When I left off the gas pedal, the car is a little jerky sometimes.

-When I'm driving down the road and shift into neutral when coming to a stop, sometimes the idle will dip down low to around 400 before it bounces back up to the normal range of around 800-900 or so.

-Sometimes when I'm just stopped and idling, the car idles perfectly smooth, but the rpms will blip up on its own. I forget how long it happens for, but it's abnormal.

-Also when shifting, the car just feels a little abnormal, shifting is a little less clean, I think it's because I'm letting off the throttle, and the car can be slightly jerky when I do that.


A little more info...

-3 or 4 weeks ago I'm driving down the road, car randomly starts jerking a lot, throws a cel. I pull over, pull the code, p0172 for one of the banks running rich.

-I'm able to get home, the car stops jerking, but I have to give the car more throttle when starting in 1st so that it doesn't stall.

-FSM says check intake leaks, check exhaust leaks, check maf sensor, and fuel pressure.

- I doubt it's a dirty maf, I've cleaned that a few times this year with maf sensor cleaner. After almost 230k, I buy a new oem Subaru maf sensor thinking maybe it's bad. Car drives better, don't have to rev high in 1st to start and stuff.

-upstream o2 is a year old NTK sensor. This problem happens with that sensor, and my old OEM sensor which is still good, I just got rid of it a year ago because I thought it's why I was getting 20-22mpg, when really it was a dirty maf causing that.


-Could a leak before the upstream o2 sensor cause this, leaking exhaust manifold gaskets?

-throttle body is clean


-trying to make my own diy smoke machine to do a smoke test, but can't find a suitable smoke source yet


-ecu has been reset multiple times. battery and alternator test good.

-spark plugs look good, wires test within spec for resistance, coil pack tests within spec for resistance. I don't know if they could still have an issue? coolant temp sensor seems fine using my cheap obd2 reader


Edited by apexi
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I assume you see the yellow pieces as "dampers", it's just quick-release connectors that you need a special tool, to separate.



The return line is to return unused fuel from the pressure regulator to the tank.



Have you checked/replaced the donut gaskets? (search for that, and you'll find what it's about) They might give quirky behavior.



Other items on the list that can give strange effects:


  • One bad injector that sometimes works correctly, sometimes not.
  • Bad fuel pump or pressure regulator.
  • Bad/sticking AC clutch.
  • MAP sensor sticking/sluggish. (Manifold Air Pressure)
  • Valve clearance.
  • Sticking EGR valve (if you have one).
  • Throttle position sensor bad.
  • Some strange TGV issue that don't throw a code.
  • General vacuum leak, possibly on the opposite side of the bank running rich.

A smoke test is a good idea, check around to see if any shop can help you with that, it's probably easier than trying to make up something yourself.



Also when idling, spray suspect joints on the intake with brake cleaner and see if the idle changes. Both cold and warm engine.



No definitive answer though. Do some logging if you can.

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Thanks for the reply. The factory service manual calls the things with the red boxes around them "dampers". I've done some reading on them, so now I have a better understanding on what they do. Supposedly they'll start making a tapping or knocking sound when they go bad. I tried to listen to mine tonight, but it's so hard to tell with how noisy these engines are..


I had my fuel pump assembly replaced 1 or 2 years ago by a Subaru dealership, so that's probably good, but anything is possible.


I quickly searched donut gaskets, and searching brings up the only one I know in the exhaust system. I think mine is still good, I replaced it 1-2 years ago when I did my center differential.


Other good ideas as well, I still have some more troubleshooting and investigating to do.


After going on a test drive, I was also sort of wrong about one of the symptoms.

- Car is actually the most jerky feeling when I give light throttle, not so much when I take my foot off the gas.


It stinks not having many diagnostic tools at my disposal, it makes me want to just throw parts at it, which I know I shouldn't do. I'll look into other ways to log some data though, that's not something I'm super familiar with, but I'm sure I can figure it out.


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Thank you for the reply. My legacy is a non-turbo, and I think I found the problem... sorry for the length of this. I'd rather give too much info/detail than too little.


If you want to avoid my rambling, the bolt that holds the pitch stop mount to the firewall was loose. I recorded a video, because I was going to ask you guys if it was normal or not.


When looking at the bolt, everything looked fine, plenty of threads sticking through on the other side. But when I went to try and tighten it, I was able to tighten the bolt maybe 2 full turns, I can't remember. So now I know, no, that's not normal.


Around a month ago when I was out of state, I had a dealership replace my clutch. I've heard that for experienced techs, pulling the engines in these cars is pretty fast and easy to do. So to try and save the tech time, I let the service advisor know that the front right cv axle might be very hard to get out of the transmission, and they might just want to pull the engine right off the bat to save time.


At the time, I had a 2 year old aftermarket "new" cv axle installed. When I installed it, it would go into the transmission, but there was resistance...Right then and there, I should have stopped, inspected the splines and circlip. But no.. I'm an idiot. I thought well, maybe this is normal for an aftermarket "new" axle. Using a rubber mallet, I was able to lightly tap it into the transmission to get it fully seated. It's also worth noting that when it was halfway in the transmission, I tried to pull and pry it back out to start over, thinking something's not right.. the axle wasn't having it, so I just kept tapping it in. That's in the past, I've now replaced that axle, and I decided to attach pictures of my diy axle puller in the highly unlikely case that anyone ever needs to pull a stuck axle from our cars... I know, I know.. in our cars, I don't think they should ever be stuck like that.


Anyway, back on topic... If you were wondering, why was the bolt loose to begin with? I think the tech just forgot to fully tighten it after reinstalling the engine. No big deal, stuff happens. I'm not smart enough to know why that could have caused some, and maybe even all of my issues, but it seems plausible. When I would let off the throttle quickly, give the car a little gas, and when shifting, I'm sure the engine probably wanted to tilt forward and backwards.. maybe the play in the mount was causing the throttle body plate to move ever so slightly? Maybe it was registering some knock? Don't know.. I only did a 15-20 minute test drive, but I think everything is good now.. I'll update this if that changes.


the youtube video I copied to make my axle puller.


*I used a different electrical box than he did, I used this one below. I used tin snips to cut through it, pull it open so that it could slip over the axle, and then the clamp was used to close the box once it was over the axle. Surprisingly hard to pull the box open, and close it after it was cut open, they're strong.




Edited by apexi
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  • 1 month later...

Replaced all three exhaust manifold gaskets, because I thought there was a chance the ones between the engine and exhaust could be leaking. Cat was replaced around 5 years ago at 135k or so, and the engine had recently been pulled, so I was worried about the condition of those 2 gaskets. The tech put rtv on the two gaskets that go between the engine and exhaust, which I appreciate to prevent leaks, but those gaskets were pretty old (10yr/230k) and in rough shape, so I figure why not.. No difference after that, didn't really expect one. Seemed like shifting might've been smoother, but I think it's in my head.


I hate the idea of just replacing parts when they test good. But I'm just a regular diy'er, so I don't know if these parts could still be bad even though they pass resistance tests.


Replaced my 5 year old oem wires that had around 120k on them with new oem wires. The resistance of my old wires was fine, but I'm not gonna complain about $50 on wires every 5 years and 100k or so.


Replaced my oem ignition coil after 230k/10yr even though the resistance was still in spec. But again, not sure if it could have been bad in some other way even though I didn't have any misfires. Picked up an ngk coil pack, which is an oem Subaru/diamond coil in a ngk box. I went that route after reading a single bad review on amazon where a guy said his oem coil died after 1 year and 12k. I don't trust everything I read, but I admit it made me nervous. I like that ngk offers a 3 year warranty over Subaru's 1 year warranty. I would be super mad if I paid over $125 for an oem coil, and have it die shortly after the warranty expired.


I also replaced my spark plugs. That was kind of painful because my plugs weren't super old, maybe 15k-20k if I had to guess. I think I paid $23 for the plugs, and figured why not to have a new coil, plugs, and wires.


Anyway, long story short, I still sometimes get the rpm drop to around 300-500rpm after shifting into neutral when coming to a stop. The car never stalls, it always recovers, so it's just an annoyance. No new codes, no misfires, nothing. At least the shifting jerkiness is fixed. I think that was mainly the loose dog bone/pitch stop, but it seems like the coil/wires/plugs helped too.


At this point I'm basically giving up and saying whatever, I just wanted to update this in case someone else comes across it in the future. I've definitely put the parts cannon down for now, I'll probably just end up testing some of the sensors or checking for vacuum leaks if I feel like torturing myself by toying with my car in the freezing cold. I'll update this again if anything changes.

Edited by apexi
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  • 2 weeks later...

I think I fixed the problem of my rpm's dropping too low after shifting into neutral when coming to a stop, bad neutral position switch that lives in the driver side of the transmission.


Read on for my ramblings..


It's a little frustrating and embarrassing that I checked this switch a month ago, and I thought it checked out fine. Truth is, I think I got the values mixed up in my head, and my switch was doing the opposite of what it's supposed to do.


You disconnect the sensor, which is next to the main engine harness on my non-turbo, under the intake tube. In neutral, the sensor should read less than 1 ohm of resistance, and when in gear the sensor should read 1 mega-ohm or more of resistance. The first time I checked the sensor I thought hey, I can remember these values in my head, so I went out to my car and checked the sensor, and thought everything was ok. Checked the sensor again a week ago, and realized that in gear I was at 0 ohms, and in neutral the readings were all over the place, but definitely not 0.


I went with an OEM sensor which goes for around $30, I had to cross reference to find an aftermarket one on rockauto which was around $21, without shipping. Subaru part number for my legacy was 32008AA141, your part number may be different.


Just to go over what I was experiencing again..

These days I find myself shifting directly into neutral when coming to a stop instead of downshifting, I guess I'm trying to be nice to my transmission since my car has 230k on it. A lot of the time after shifting into neutral, the rpms would drop down to about 300-400pm, and then bounce back up to their normal level. The car would not stall, the car would always catch itself, but it was quite annoying.


After replacing the neutral position switch, after I shift into neutral when coming to a stop, the rpms will drop down to 1000rpm (+/- 100rpm), hold at 1000 for about 1 second, and then slowly drop down to about 650rpm or so.


*I know I've switched between the words "switch" and "sensor" a lot in my replies. That's because I didn't know what this thing was at first, Subaru calls it a "switch", but I thought maybe it was some kind of magnetic sensor.. Turns out, the little black part at the end of the switch is a little plunger that goes in and out, so I guess "switch" really is the correct technical term like Subaru says?


*12/15/18: After doing more driving, the rpm's don't always hang at around 1k like they did yesterday after a lot of driving. I don't really understand, the engine is at operating temperature, outside temp is around the same, but a bunch of times today the rpms dropped right past 1k down to around 700 or so.


Edited by apexi
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Great info for the archive! This is the first I heard of someone shifting an automatic like a manual lol.


Sent from my SM-G950U using Tapatalk


Haha hey, my wimpy non-turbo legacy is a manual haha


I know it sounds weird that the MT's have a neutral position switch, but they do..


I guess I'm just trying to be nice to my synchros since I've been worried about them for a long time. If I try and shift too fast, the gears will grind and let me know the car isn't happy at all. So as long as I shift like a normal person, everything is fine.


* 12/29/18: I don't want to bump this again, so I'll just make this edit. The problem doesn't seem to be 100% fixed. It seems to be better, happens less often, but isn't 100% gone. I'll update this when/if I know more, I think I'm just sick of it and still kind of ignoring it.


Edited by apexi
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