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Old 04-24-2014, 02:08 PM   #1
G2
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Unhappy Stumped: P0171 & Evap System won't clear

MAIN QUESTION:
Anyone know of a correlation between the EVAP system and the P0171 (lean bank1) code?


Long description & details:
Before anyone says I should bring it to a shop to diagnose, I had it at my local dealer four times in the past month, and the only thing I've gotten is a broken TGV sensor from a clumsy tech, vacuum lines left off on the IM, and a bunch of high dollar estimates on guesses as to what it "could be"...seriously, like $850 to replace parts that they "think" might be related. (they also said my turbo was the reason for the surging, which they proceeded to quote me almost $1400 to replace - which was solved by a new fuel pump - see below). They won't get another cent from me! /RANT

So, I've poured over this site for 6-8 months trying to find a solution to my problem but to no avail. Including reading nearly every post in the 23-page P0171 master thread here and I'm still getting stumped.


What's unique with my P0171 issue is the EVAP system won't complete the system check.
Had it presmogged and emissions are spot on...all numbers are at or below average passing specs. No problem passing minus the CEL code P0171 and the fact that the pre-check system won't complete the EVAP system check (even after weeks of driving).
I'm wondering if they are related somehow?

Here are the details:
'02 WRX
  • Catless UP
  • Factory DP w/ cats, Catback Exh. (have catless DP I run when not trying to get it smogged)
  • Stock airbox w/ K&N panel filter, no snorkel
  • v1 Accessport (in stock married w/ cats on, stg1 w/ catless DP)
What I have done:
  • Dealer replaced fuel rails, o-rings and fuel hoses
  • Had Dealer replace ALL the vacuum lines on the engine/IM (many were hard/cracked/etc.- accell smoother now)
  • Flushed IM w/ seafoam (idles better)
  • Had dealer replace IM gaskets (no diff)
  • cleaned MAF & IACV (no difference)
  • had dealer replace turbo inlet pipe (factory unit...no change but old one was cracked near turbo)
  • Replaced exhaust gaskets (one was leaking)
  • New plugs (cleared up misfires, but nothing affecting current CEL)
  • New fuel filter (no dif, but assumed it should be done as reg maint)
  • New airbox from 05 STi (the bottom half of mine was broken at the lip that holds the tabs in place on the side closest to the engine, so I assumed it might not have been sealing correctly (another mentioned fix for the code))
  • replaced fuel pump (new warbro did wonders! cleared up the hesitation and bogging in the midrange, but didn't fix the CEL)
Most everything I've done (which are almost all mentioned as solves for a P0171 in the master thread) has made some improvement to the car and how it runs, but nothing has fixed the CEL code or the EVAP System check completion.

I have a new Denso front O2, because the CEL normally pops on long freeway drives w/ little or no throttle input and that seemed to be mentioned as a symptom in the p0171 Master Thread as a front O2, but also seeing that the EVAP system is not passing the system check after the CEL is cleared (see below) I wanted to see if anyone knows of a correlation between the EVAP system and the P0171 (lean bank1) code?

I don't want to continue to throw parts at this thing (I'm getting to the expensive parts now) and so I came here to see if anyone had any other thoughts.

Thanks for any insight anyone can glean on the situation.



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Old 04-24-2014, 02:22 PM   #2
SCwrx85
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Evap system works off of manifold vacuum through the purge control solenoid. Was that tested or replaced? If its stuck open its possible, though unlikely, that if the vent solenoid is also stuck open to pull atmosphere through the evap system. This would cause a small vacuum leak. Just a thought but you could test this yourself by jumper wire to the terminals on the purge solenoid and see if you can put air through it. Then repeat with no power. Same goes for the vent solenoid. What's the evap code? I don't think you mentioned that though i may just be blind.
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Old 04-24-2014, 02:47 PM   #3
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http://i81.photobucket.com/albums/j2...r/DSC00861.jpg

I would look and make sure this check valve is secured besides the actually purge solenoid.
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Old 04-24-2014, 03:09 PM   #4
G2
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Quote:
Originally Posted by SCwrx85 View Post
Evap system works off of manifold vacuum through the purge control solenoid. Was that tested or replaced? If its stuck open its possible, though unlikely, that if the vent solenoid is also stuck open to pull atmosphere through the evap system. This would cause a small vacuum leak. Just a thought but you could test this yourself by jumper wire to the terminals on the purge solenoid and see if you can put air through it. Then repeat with no power. Same goes for the vent solenoid. What's the evap code? I don't think you mentioned that though i may just be blind.
SC, there is no EVAP code. the EVAP precheck system just won't complete after CEL/ECU reset. The ECU goes through a system of checks after it has been reset and the EVAP system won't finish this check. It is a system that has to clear before the smog can be done, which is part of my problem.
The dealer didn't mention that the Purge control solenoid was tested specifically, but they said they had (supposed) to run a full diag on all sensors when tracking back the issues I had (both before and AFTER I had them work on the car - see broken TGV sensor).
I'll check the trobleshooting guide in the FSM on the purge control solenoid and see if that is the issue.
I do know that under sustained boost (>~0.5 BAR) it tends to loose boost, then build again, then boost drops again then steps up...only intermittent but is this possibly related?



Quote:
Originally Posted by Strider327 View Post
http://i81.photobucket.com/albums/j2...r/DSC00861.jpg

I would look and make sure this check valve is secured besides the actually purge solenoid.
are you referring to the blue one-way valve on the line? that is secure on my car. I had to push them back together after the brick-handed dealer tech left it undone a few weeks ago. But that didn't stop the CEL from popping again.


BTW, thank you guys! Will check/double-check these at lunch—guess it was a bad day to wear white to the office. :\
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Old 04-24-2014, 03:32 PM   #5
Strider327
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The one that is screwed onto the intake manifold. The black check valve.

Quote:
Originally Posted by G2 View Post
SC, there is no EVAP code. the EVAP precheck system just won't complete after CEL/ECU reset. The ECU goes through a system of checks after it has been reset and the EVAP system won't finish this check. It is a system that has to clear before the smog can be done, which is part of my problem.
The dealer didn't mention that the Purge control solenoid was tested specifically, but they said they had (supposed) to run a full diag on all sensors when tracking back the issues I had (both before and AFTER I had them work on the car - see broken TGV sensor).
I'll check the trobleshooting guide in the FSM on the purge control solenoid and see if that is the issue.
I do know that under sustained boost (>~0.5 BAR) it tends to loose boost, then build again, then boost drops again then steps up...only intermittent but is this possibly related?




are you referring to the blue one-way valve on the line? that is secure on my car. I had to push them back together after the brick-handed dealer tech left it undone a few weeks ago. But that didn't stop the CEL from popping again.


BTW, thank you guys! Will check/double-check these at lunch—guess it was a bad day to wear white to the office. :\
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Old 04-24-2014, 03:34 PM   #6
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Did the dealer actually hook up the EVAP system to a smoke machine or other leak checker down near the tank?
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Old 04-24-2014, 04:01 PM   #7
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How does the car run? I've had a few where the MAF sensor is bad causing a lean code. Usually it will also run a little ratty especially under boost. If it's not running right, try driving it around with the MAF sensor disconnected. You will set a few more codes but the car will go into a type of limp mode and base fuel trim on just the a/f sensor readings. If it runs nomal again then you know where the problem is. As far as the evap monitor not setting its possibel the ecm won't run the test if fuel trim is too far off. If there was a problem in the evap system there will normally be a code.
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Old 04-24-2014, 04:10 PM   #8
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Quote:
Originally Posted by Strider327 View Post
The one that is screwed onto the intake manifold. The black check valve.
checked and all lines are secured to/from IM and check valve. Unless it's directional and could be in backwards(?)...I didn't look for a direction arrow.

Quote:
Originally Posted by arghx7 View Post
Did the dealer actually hook up the EVAP system to a smoke machine or other leak checker down near the tank?
highly doubt it...they're about as helpful as a gorilla for making pottery.
Quote:
Originally Posted by oldandbrittle View Post
How does the car run? I've had a few where the MAF sensor is bad causing a lean code. Usually it will also run a little ratty especially under boost. If it's not running right, try driving it around with the MAF sensor disconnected. You will set a few more codes but the car will go into a type of limp mode and base fuel trim on just the a/f sensor readings. If it runs nomal again then you know where the problem is. As far as the evap monitor not setting its possibel the ecm won't run the test if fuel trim is too far off. If there was a problem in the evap system there will normally be a code.
car right now is running the best it has in a while. fuel trim is never more than -0.8 to -1.6 and since the install of the fuel pump i don't think i've seen it less than zero (see bottom right "F/T" dial on the OBD monitor screenshot from my phone it's at zero with no peak (red arrow) set. that was after driving it about 50 miles). will drive it around at lunch w/ the MAF sensor unplugged and see what I get.

Thanks again all!
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Old 04-24-2014, 11:10 PM   #9
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My bad on missing that part of your post i apparently blasted past it. I agree with the fact that usually an evap malfunction will set a code, however, I've learned there are no absolutes in this industry. I assume you are looking at long term fuel trim and if they are normal then its unlikely to actually be a vacuum leak. the boost surging up and down is on the other hand a symptom of a vacuum/boost leak as well as many other things. Performing a smoke test on both the intake system and evap system would definitely rule this out or confirm. The only other things that could cause that code would be an incorrect o2 reading, which a graphing log of the o2 sensors would reveal, or a failed ecu. I'd be hesitant to condemn the maf since it affects both banks and should set both lean codes. That being said anything is possible but there are test procedures that can be done to confirm or eliminate possible causes. If you don't have the equipment to diag this yourself i would find a competent (not the dealer with the tard techs) technician who can perform these tests. A lab scope is almost going to be mandatory in this case.
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Old 04-25-2014, 12:32 PM   #10
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Quote:
Originally Posted by SCwrx85 View Post
My bad on missing that part of your post i apparently blasted past it. I agree with the fact that usually an evap malfunction will set a code, however, I've learned there are no absolutes in this industry. I assume you are looking at long term fuel trim and if they are normal then its unlikely to actually be a vacuum leak. the boost surging up and down is on the other hand a symptom of a vacuum/boost leak as well as many other things. Performing a smoke test on both the intake system and evap system would definitely rule this out or confirm. The only other things that could cause that code would be an incorrect o2 reading, which a graphing log of the o2 sensors would reveal, or a failed ecu. I'd be hesitant to condemn the maf since it affects both banks and should set both lean codes. That being said anything is possible but there are test procedures that can be done to confirm or eliminate possible causes. If you don't have the equipment to diag this yourself i would find a competent (not the dealer with the tard techs) technician who can perform these tests. A lab scope is almost going to be mandatory in this case.
Thank you for the reply. Since the car has over 150K on it anyway, it sounds like replacing the front O2 is not going to hurt at this point (was hesitant, since I can still return it until I actually install it). And while replacing the TGV sensor last weekend I did notice two wires on the O2 lead have electrical tape on them where it looks like someone removed the insulation in a small spot to tap into the lines (perhaps for an on-the-cheap A/F gauge install?).
O2 doesn't take too long as long as I can get by my buddy's shop with a lift.
If that isn't going to clear it up I'll look into the smoke tests and a full scope diag. (both of which I'll have to take it to my local shop—just trying to do as much as I can on my own)
Hoping this is the light at the end of the tunnel...
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Old 04-25-2014, 09:12 PM   #11
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So the main focus is the evap system isn't completing the check? Have you done the 50mph in 5th gear step? This will work best late night with little to no people on a highway. Bring car to 50 mph and hold for approximately 5 miles. Try not to vary throttle, cruise control will not work. That should force the ecu to do the check. The flatter the highway the better, any load (boost) will change the parameters and will not work either. Sounds impossible but it can be done, I've done it many times on test drives.
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Old 04-25-2014, 09:42 PM   #12
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ya got a busted vac hose between the evap purge solenoid valve and the intake
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Old 04-25-2014, 09:59 PM   #13
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ya got a busted vac hose between the evap purge solenoid valve and the intake
Kind of what i was thinking...smoke test should reveal that though.
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Old 04-25-2014, 11:27 PM   #14
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Originally Posted by SCwrx85 View Post
Kind of what i was thinking...smoke test should reveal that though.

maybe...but the issue is almost certainly in that section of the system

if it only leaks when the purge valve is open....its hard to find

or maybe the valve itsef is bad/leaking
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Old 04-26-2014, 08:45 AM   #15
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A good scan tool would allow him to command it closed. I'd disconnect the line opposite the one going to the intake during said smoke test and command it shut. At that point you should not be seeing any more smoke. If it was a failed valve our stuck open it should be instantly visible.
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Old 04-28-2014, 11:53 AM   #16
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Quote:
Originally Posted by SCwrx85 View Post
A good scan tool would allow him to command it closed. I'd disconnect the line opposite the one going to the intake during said smoke test and command it shut. At that point you should not be seeing any more smoke. If it was a failed valve our stuck open it should be instantly visible.

ya know something......im the ONLY ONE that i know that has his own scan tool

the only one that isnt a dealer tech, that is

quite surprising as a GOOD scan tool can tell you so much and ELIMINATE guesswork

now...the scan tool YOU are talking about...that can 'command' things...is $,$$$....not $$$

and i HAVE seen subaru select monitors.....for sale at times....which cost about the same as the $,$$$ scan tools
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Old 04-28-2014, 01:04 PM   #17
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I agree with you on cost stand point. I used a snap on modis for about 5 years until they worked the bugs pout of the verus pro and now i have that. Dealer gave me a hell of a deal on it so i pulled the trigger. I'm glad i did as it is amazing but with a retail of over 10,000 without my trade in it would've hurt big time. I also agree with you on your perspective towards diag. There is NO substitute for having the right tool for the job. If you want to shot gun parts at it and spend hundreds of dollars needlessly have at it but that's not how i do things. nice to see some one else that takes it seriously on here with all the people posting random garbage about "help me diag my car online the shop wants to charge me $100 and i don't wanna pay".
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Old 04-28-2014, 01:27 PM   #18
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also...do NOT expect anybody here..well...99% of them...to have anywhere near the troubleshooting skills that YOU dont even THINK about

most the guys that really know their **** hang in the built motor and other more technical forums

the factory 2.0 forum is become...well....
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Old 04-29-2014, 03:28 PM   #19
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thanks gentlemen! I was kind of out of tinkering the past few days with my birthday and family fun.
Going to put my nose to the wheel this week and try to secure the issue.
If I cannot find a local shop that has the control tool for the sensors and a smoke testing method, I'll have to drive to get to the nearest tuner that I know can help.

Anyone have a recommendation on where/how to find the OE vacuum lines for replacement (once I find the culprit)?
I've tried to look up vacuum lines on subaruparts.com and other OE parts sellers and none will bring up the vacuum lines (or even the EVAP purge sensor for that matter—at least in every config i can think of to search for), and the local dealers are not much help around here (see above).
Thanks again!
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