Momwagon is angry

Discussion in 'Modifications And Maintenance' started by subie-roo, Jul 7, 2019.

  1. subie-roo
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    subie-roo Well-Known Member

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    Recently I’ve had some weird oil consumption issues and concerning results from Blackstone. I checked a few things and made an appointment with JM on the 15th since I was gonna be in town.

    Apparently the Momwagon doesn’t want to visit and started getting moody with me. In addition to some play in my carrier bearing (new driveshaft on its way) I’m seeing occasional lean AFRs while cruising, worsens with slight acceleration, smoothes out under throttle. Gas is good, my local station is testing at E80-90 for the past two months. Checked for vacuum leaks, couldn’t find any. Decided to dust off the AP and plug her in to do some logs, DAM at .750, UGH! Got some fresh E85, reset my ECU and did some logging. Random roughness on all cylinders, worse in lean conditions. WOT logs look great, no roughness and zero FBK.

    Plugs changed 3k ago, gonna try swapping my coilpacks with known good ones. Most components have 15k on them, but some sensors and whatnot are original, with 124k or so.

    Thoughts and/or recommendations? I am not savvy with this **** by any means, but I’m trying to narrow it down and have been scouring forums, and it seems it could be many things. Thanks in advance for the help and/or the sarcastic comments ;)
     
  2. pillboy
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    pillboy Well-Known Member

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    Because Subaru.
     
  3. Mnelson
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    Mnelson Active Member

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    Full disclosure, I am by no means a professional and the following is largely based on my personal understanding.

    Electrical
    : First off, a super simple test would be to do a battery/alternator test at a parts store like advance auto. Also checking that the fuel injectors and coils have good solid grounds as well as testing resistance between the battery terminal and various parts of the block. They make "block grounding" kits to help with poor connections.

    Fuel: Might also be worth sanity checking the fuel pressure. I've read somewhere that LGT and OBXT around your year had a relay voltage issue where the wire to the pump would go bad and the fuel pump ran slower that it should. There could also be evap/filter restrictions that are worth checking out too.

    Oil: What did Blackstone say that was concerning? Blackstone didn't find any fuel or moisure in the oil that came out of my blown ej257 which had signs of moisture build up, so take their reports with a grain of salt. Do you hear any new/abnormal noises? (Because that's probably normal subaru junk) And how much consumed per mile? I found my old stock block to lose about 1-2q every 3k. If you can, get a compression and leak down test done too. Blow-by on e80 isn't ideal for the bearings and will cause oil to thin/sheer faster.

    Exhaust: I would also check for exhaust leaks, especially near the front o2, as that can throw the AFR value off. Also check grounding and resistance there too. Logs of the sensor values can help troubleshooting here too.

    Tune: I have seen multiple instances where tuners will take timing away in the cruise range (CL 0.7-1.2 / RPM 2000-2500) that appear to help with earlier spool, but have a side effect of phantom knock on the freeway. This may be related but its hard to tell without logs. It isn't a bad thing persay, but it can trick the ECU into thinking there is an issue that may cause the ECU to react and make the symptoms worse.

    Other stuff: Didn't your car had TGV deletes? If not, double check that there isn't a leak near the electric motors on those. I once had that issue on my sti.

    Lastly, I can look at any cruise logs if you send them to me. There are a few things that I look at that aren't in the default data log so message me if you would like to work together on that part.

    ----
    Justification/Technical stuff:
    Electrical: It seems irrelevant but it will tell you if your alternator isn't providing enough power in the low rpm range (cruise). Coil packs need to fill up like those buckets of water that tip over at the water park. The time it takes to fill up is called dwell and the less power the coils get, the longer it takes to fill up. If the coils aren't ready by the time ignition happens, the spark will be weak, late, or non existent (I cant remember which is most common).

    Explaining DAM: There is a base timing table (the care runs off of) and a "DIT" (dynamic ignition timing) table of extra timing that can be added to the base timing. DAM (dynamic advance multipler) is a value (0-1) that is multiplied with the DIT and added to base. This number isn't a value of how bad a car is running, its an indicator that the car doesn't want the extra timing, right now. Most frequently when something "bad" happens but not always. When the ECU is reset, the DAM returns to 1. If the issues are persistent regardless of dam value, it may not be related.

    Knock: Feedback knock (FBK) is just timing pulled under load, which acts as a safty net to prevent future knock events. Fine knock learn (FKL) is when the ECU sees FBK in the same spot over and over, so it saves that value. FBK is like short term fuel trims and FKL is like long term fuel trims, but for knock. Both FKL and FBK operate on a x=rpm y=load axis and is only applied to certain rpm/loads. DAM is similar to FBK and FKL but will lower its value if the ECU records a threshold of knock over a certain period of time.

    Justification of phantom knock/tuning: I think the "phantom knock" is actually post-ignition or roughness that is picked up as knock by the ecu and pulling more timing will make the symptom worse. Theory - Less timing may result in lower torque output which may cause the ecu to open the throttle plate more which might explain the AFR spike. Freeway cruise is interesting because your car is under just enough load that a hill or gust of wind can put your ecu into "under-load" range (CL > 0.70). The ECU only pulls timing (FBK/FKL/DAM) above a load threshold seen just above cruise. Another theory is that the depending on the fueling strategy of the tune, un burnt fuel could be throwing AFR off or igniting/combusting in the exhaust manifolds.

    Justification of fuel pressure check: Most cars rely on the mechanical fuel pressure regulator to set the correct fuel flow to the engine based on manifold pressure while the fuel pump is set to a set speed (low/med/high) based on rpm/load (I believe). The pump should always provide more fuel pressure than the engine needs so the regulator can lower it to the 32psi(?) the engine is calibrated for. If the voltage is low at the pump, its going to provide less fuel pressure across the board. If the pump is providing less than 32psi(?) the injectors may be starving, possibly when it needs to switch from low to med during cruise? If you have a fuel pump that can deliver way more fuel than the engine consumes under full load, its possible these symptoms would be masked during WOT.
     
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  4. subie-roo
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    subie-roo Well-Known Member

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    Thank you for the detailed information. The MAF sensor was the culprit, AFRs have returned to normal and all my logs are free of cylinder roughness through multiple driving conditions. I know I've talked with you in the past about the "phantom knock" I experience, and it seems like it may be due to transmission noise. Replaced the sensor and it has improved greatly but still pops up in high numbers here an there, seems less prevalent when the vehicle is warm.

    My Blackstone reports keep showing an increase of wear metals, which is concerning considering the age of the build and my change intervals 2-2.5k, I also a seeing oil consumption, I had zero consumption the first 8-10k on this motor. I am still waiting on my most recent sample to see if they are still increasing.

    I have an appointment with JM tomorrow to get it looked at to try and determine the root cause of the oil issues and Devin is going try and pinpoint the phantom knock issues.

    Hope to see you at LAX camping if we make it.
     
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  5. Mnelson
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    Mnelson Active Member

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    Good to hear you got further on that. I thought about suggesting a drive without the maf but worried it could Bork things more due to the tune.

    As for the noise, my clutch and injectors are literally audible and a large source of my paranoia yet I see zero phantom knock.

    Wear metals going up is a good indicator. Hopefully you arent seeing much silver increase. That was a huge indicator that my bearing was going to fail just before it did.

    Best of luck at JMs. I'm positive Jessie will take care of you guys so I'll EXPECT to see you at lax. :)
     
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  6. subie-roo
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    subie-roo Well-Known Member

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    A good indicator that something is wrong? I have increased copper, aluminum and iron. Zero silver though. Besides that the oil looks good, still waiting on my most recent sample. Been hearing some nonsense in the forums about ester based oils being better for E85, but I don’t know if I can warrant the cost of Moutl 300V with the short change intervals.
     
  7. Mnelson
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    Mnelson Active Member

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    Used the wrong word. Should've said measurement. I've stuck with car quest (rebranded valvoline) and change it no later than 3k with pretty good luck so far. Cheap and doesn't seem affected by e85. Ymmv
     
  8. subie-roo
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    subie-roo Well-Known Member

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    UPDATE. Visit at JM did not go as hoped, low compression on cylinders 1 and 4. Underlying cause unknown but likely the lean fueling conditions I had been experiencing contributed to it, wont know for sure until its torn apart.

    On the bright side I can stop wondering whats wrong with it :(
     
  9. subie-roo
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    subie-roo Well-Known Member

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    And shoutout to @JasonoJordan for saving the day and getting me back to my in-laws from JM - I owe you a few beers!!
     
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  10. Krazylegz1485
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    Krazylegz1485 Well-Known Member

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    Holy sh!t... Moment of silence will be had this evening. Sorry to hear.
     
  11. JasonoJordan
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    JasonoJordan Well-Known Member

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    No problem. Eager to hear what the final cause of the issue is and excited to see where the next build takes you.
     

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