This Normal? - Page 2
+ Reply to Thread
Page 2 of 2 FirstFirst 12
Results 16 to 26 of 26

This is a discussion on This Normal? within the Tuning: Electronic Engine Management forums, part of the Tech & Modifying & General Repairs category; I think that I'll first try the water/soap version to see if the vacuum sucks it in and makes a ...

  1. #16
    Registered User Obeisance's Avatar
    Join Date
    Apr 2012
    Location
    not Ann Arbor
    Posts
    315
    I think that I'll first try the water/soap version to see if the vacuum sucks it in and makes a noise.

    Also, as a second check, I drove for another 30-40 mins and there was another small change in the fuel learning value (added to above link) in learning view.

    Before maf cleaning, after a 30 min drive, then another 40 min drive.
    A/F Learning #1:
    0 - <5.60 5.60 - <10.00 10.00 - <50.00 50.00+
    11.67 4.49 3.22 -2.15
    11.47 3.81 2.54 -2.25
    10.89 4.3 1.66 -2.25

    Perhaps it is slowly coming down?

    Edit: later checking shows that there is no slow reduction of the fuel learning
    Last edited by Obeisance; 02-22-2014 at 03:22 PM.
    David - '05 WRX

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #17
    Registered User Obeisance's Avatar
    Join Date
    Apr 2012
    Location
    not Ann Arbor
    Posts
    315
    Alright, I have now checked for vacuum leaks with soapy water, but saw and heard nothing out of the ordinary. I am viewing this problem as a "perceived problem" since I would not have recognized it without trying to datalog.

    I wonder if fuel composition changes (compared to the injector calibration) could cause my issues. For instance, I've read that winter fuel has added butane, and I'm pretty sure that my 93 octane fuel has 10-15% ethanol. These additives have different densities, and I assume that pressurized fuel is added with a simple pulse width modulation of injectors, so the different density (and possibly compressibility) of the additives should change the actual amount of fuel added at a given PWM (compared to what the injectors were calibrated for). This may lead to a difference between the amount of fuel needed to maintain the 14.7 A/F ratio read by the sensor and the amount of fuel predicted to be needed by the MAF/injector calibrations (and compensated for by the A/F learning). Does what I'm thinking make sense to you all?

    I do not expect that I have an intake leak post turbo, since my car is able to make full boost, and uses 90+% duty cycle on the wastegate (I think if I had a post-turbo leak, that I couldn't build boost easily, or the wastegate would stay closed for more time to help keep the boost up). Maybe there is a tube leaking somewhere, but soapy water didn't reveal anything.

    For now, since I do not have driveability issues, I will continue to monitor the A/F learning periodically without paying someone to diagnose my car.

    My A/F learning is now over 12%
    Last edited by Obeisance; 02-22-2014 at 03:24 PM.
    David - '05 WRX

  4. #18
    Registered User
    Join Date
    Feb 2014
    Posts
    32
    Quote Originally Posted by Obeisance View Post
    Alright, I have now checked for vacuum leaks with soapy water, but saw and heard nothing. I am viewing this problem as a perceived problem since I would not have recognized it without trying to datalog. I wonder if fuel composition changes could cause my issues. For instance, I think that winter fuel has added butane, and I'm pretty sure that my 93 octane fuel has 10-15% ethanol.
    I am fairly certain law requires no more than 7% ethanol or so. Never heard of butane in auto fuel.... I have a good friend that works for one of the largest if not the largest gas and oil companies on the east coast and they don't use butane, although there are certain amounts of diesel and other oil based fuels that are allowed in very very negligible levels.

    Sent from my SM-N900V using Tapatalk

  5. #19
    Registered User Obeisance's Avatar
    Join Date
    Apr 2012
    Location
    not Ann Arbor
    Posts
    315
    Here's what I've found for now:
    1) Michigan fuel commonly includes a fair amount of ethanol (I took this photo at my last fill up)


    2) I found various studies about how the addition of ethanol to fuel influences fuel learning, and liked the plots out of this one:
    http://www.crcao.org/news/Mid%20Leve...G%20050510.pdf

    A short version of my interpretation is that the inclusion of ethanol into fuel does increase the fuel learning. However, if this were a common problem in subaru wrx's, someone else on the forum would have noticed, right? I'm not in a trouble range of the LTFT's yet, but I do worry that my stock car reaches 90+% injector duty cycle on a hard pull. Again, I'll continue to monitor my fuel learning and see if things worsen.
    David - '05 WRX

  6. #20
    Registered User Obeisance's Avatar
    Join Date
    Apr 2012
    Location
    not Ann Arbor
    Posts
    315
    Well, I've been watching my fuel learning, and it hasn't gotten better as temperatures have increased and as fuel has (I presume) switched away from the winter blend. My fuel economy, however, has returned back to summer-like levels of 25-27 mpg. I do not expect that the moderate fuel learning impacts the fuel economy, though.

    I have noticed another symptom of a possible vacuum leak: when I lift off of the throttle at cruising speed and rest my foot over/on the brake pedal, I can feel a delay in the time from when I let off the gas to when the brake boost begins to build (I can feel the pedal soften and pull away after a delay)- this has two implications: 1) it is potential evidence for a vacuum leak; 2) it is potential evidence for the danger of a vacuum leak beyond engine damage (if I run out of injector overhead at high load). When I have suddenly needed to brake, I feel like my pedal was far too hard and my brake response was too weak for how hard I was pushing.

    Thus, I'm planning on performing a better leak test, as has been suggested to me, next weekend. Here's the plan:
    follow instructions from some other threads to plug off some lines:
    Another DIY Boost Leak Tester - Home Depot and AZ parts - NASIOC
    Just completed the DIY "find your leak" tool. - NASIOC
    Boost leak test instructions

    Their instructions for making the tester mislead me: I tried to purchase 2" PVC components to attach pre-turbo, but these were the wrong size. The inlet after the post-MAF elbow has an outer diameter around 2 7/8" - so I purchased a 3" PVC cap (larger than 3" in both diameters), a 4" to 3" rubber downspout adapter, a couple of worm gear clamps, and a threaded valve stem.



    For the test, I'll use the pressure regulator on an air compressor to pressurize up to about 15 psi and I'll monitor pressure leaking vs time with romraider. I plan to spray my soapy water on parts again, and hope to find a leak.

    My end goal is to repair the leak and observe better brake boost response and reduced fuel learning at low engine load/engine air flow.
    David - '05 WRX

  7. #21
    Registered User wreckingball man's Avatar
    Join Date
    Jul 2012
    Location
    Rocky Top
    Posts
    2,298
    Sub'd for later.

    Sent from my Lumia 900 using Tapatalk

  8. #22
    Registered User Obeisance's Avatar
    Join Date
    Apr 2012
    Location
    not Ann Arbor
    Posts
    315
    Well, I guess I wasted a bunch of time. I think that I didn't properly perform the pressure test, since I'm not sure that I was able to get the system pressurized high enough- romraider wouldn't give any change in "manifold relative pressure direct," instead, the boost error field would change (up to -7 to -8 psi). I used a pressure regulator on the air compressor (and verified that I provided 17 psi by filling and measuring another tank), but only applied air for 30 sec or so at a time. In the end, I couldn't find any appreciable leak- and nothing changed in my LTFTs. Here's the long version:



    First, I began by removing the intake parts which were in my way. Next, I unplugged a bunch of tubes from the low-pressure side of the intake. I've circled much of what I removed in the above image.

    I had to unplug tubes from the breathers on the heads (and the crossbar between them), some (evap control?) valve on the front of the intake manifold, and some tubes around the PCV (which required removal of the intercooler- this is a pain since it was nicely seated at each fitting). I found yellow, watery froth in the breather line (image below), and cleaned this out before re-assembly. I assume this is normal.



    Getting to the PCV was a pain. I removed and cleaned it (it rattled when shook from the start, so all is well).



    Then, I re-installed the PCV "T" fitting, and plugged off the lines which lead to the intake:



    I used soft plugs, and random metal rods which I found laying around to plug the tubes.



    Once all the hoses were plugged, I put the intercooler back on, and was ready to pressurize the system.



    Once pressurized, I could see a few spots on the low-pressure side of the intake leaking.



    I zip-tied this off, but assume that it is not likely the source of my LTFTs/a leak.

    There was also quite a leak coming from this strange sensor:



    Well, I removed the sensor, and checked the internet to see what it was: I found that this simple sensor adds 15 HP. I'm glad that Subaru saw fit to add this, and am wise not to remove it. -_-




    I then took it all back apart, re-connected the fittings and re-assembled it. Then I went for a drive and took datalogs. Mostly I was checking for changes in A/F learning, and to see if I could get peak boost (hence had properly seated the intercooler).

    Boost was able to get to about 13.6 psi (below 55 mph, too), so I'm not terribly convinced that I have an appreciable leak.



    Also, the A/F learning before and after the run seemed identical. Thus, I've not gotten closer to finding my "problem."
    Last edited by Obeisance; 04-27-2014 at 06:22 AM.
    David - '05 WRX

  9. #23
    Registered User Obeisance's Avatar
    Join Date
    Apr 2012
    Location
    not Ann Arbor
    Posts
    315
    Well, I've not done anything to help this problem (assuming that my pressure test disassembly and reassembly didn't make an appreciable change), but the warming temperatures seem to have impacted my long term fuel trims:

    A/F Learning #1:
    0 - <5.60 5.60 - <10.00 10.00 - <50.00 50.00+
    8.35 6.05 4.3 -3.13

    near idle, it went down from 11-12 to around 8. hmm
    David - '05 WRX

  10. #24
    Registered User
    Join Date
    Nov 2009
    Location
    Brisbane, Australia
    Posts
    2
    I figured I'd jump in here and hijack this thread as well, since it's sort of similar... Below is my copy-paste from a few places where I'm seeking help with a similar issue,Basically for a TL;DR version; Brand new engine, engine ran fine (700km on it), was removed, re-installed with no other change, everything was hooked up and checked, and now have symptoms of a vacuum leak. Everything checked and no leaks, thoughts?



    Hi all

    Having a bit of drama with the STI at the moment.

    Replaced the engine a few months back after losing Cyl 4 and had some dramas that seemed like a vacuum leak (high fuel trim, stuttering on rev-down, stall-like symptoms at stops, etc) - turns out it was, I'd left the fuel vapour purge hose disconnected under the manifold.

    Anyway, fast forward to now and it's been running great, I had fuel trims down to ~-2% across the board. Randomly had a rattle/knocking from the engine and vibration in the clutch pedal so pulled the engine last week and found one of the flywheel bolts had come loose (not undone, just loose). So re-torqued everything and had a quick look over the engine and nothing else seemed out of the ordinary.

    Put the engine back in and everything works fine, however know I'm getting maxed out fuel trims (ie +15%) at idle(0-5.6gm/s) and at cruise (10-80gm/s) and around +5% at low laod (5.6-10gm/s) (obviously lower as it's such a small target and is rarely hit).

    I've gone over the entire engine bay and checked every vac connection, gasket, exhaust joint, intercooler clamps, etc etc. Nearly replaced every single vacuum hose and have gone over the engine with flammable spray listening/watching for changes, have hooked up an air supply to the manifold and sprayed every connection/etc with soapy water and have had no results.

    It's still hitting around -19inHg at vacuum, but does have a slight stutter coming to a stop and vacuum fluctuates - hence why I suspected a vacuum leak.

    What stumps me is that it was running *perfectly* and was then removed/reinstalled, and the only things that were touched were all reconnected.

    I've pulled the intake manifold off again just to double check everything but it's all copasetic and I'm just going to keep chasing my tail here.

    Any thoughts/things to check would be great

    Cheers

    Al

  11. #25
    Registered User Obeisance's Avatar
    Join Date
    Apr 2012
    Location
    not Ann Arbor
    Posts
    315
    I found another lead on the front page of NASIOC:

    Mass Air Flow Sensor (MAF) FAQ: Read as you know less than you think you do! - NASIOC

    Perhaps the MAF sensor is beginning to wear out (and the ECU is using the A/F sensor to compensate)... I'll have to see how I can try an diagnose this...
    David - '05 WRX

  12. #26
    Registered User
    Join Date
    May 2014
    Posts
    4
    Good stuff, subbed for later

+ Reply to Thread
Page 2 of 2 FirstFirst 12

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself. We strongly suggest that you stay away from using aol, yahoo, msn, and hotmail accounts. Sometimes the mail server blocks the emails from our server. As a result you will not receive any notifications including the confirmation email.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •