85T Arbitrarily Lean

  • #1

    85T Arbitrarily Lean

    So, after my long endeavour with chasing a faulty fpr, it has been running beautifully ever since (about x months can't remember). Recently, on my way to visiting family, I started going lean out of nowhere on my wideband and, when trying to accelerate, it started to backfire really bad and struggled to go past 55 without downshift.

    Fast Forward a day: dad and I found a vacuum leak from the coupler after the afm slightly opened and a crack in one of my hoses, fixed those up and seemed to not have the leak anymore. Still struggled to accelerate some but not as bad… But still backfires. I changed the fpr as when I disconnected it from the vacuum port idle afr was where I normally see it. Twas good on that, ran better but still rough.

    Fast forward some more days: found I was misfiring in cylinder 2 because of. Spark plug looking pushed into itself and the porcelain moveable, also the wire snapped. Swapped those out and everything was immaculate! Afr was as it use to, accelerated like a dream, boosted like nobody's business. Everything perfect.

    Fast forward to today: Struggled to start, when it did was ungodly lean (pretty sure my O2 couldn't read more than 22.4) and tried to die on itself. Feathered the pedal to try to keep it up and still struggled. Found a sensor that disconnected (forget which one, I think the IACV? 19mm long thing with a spring and thing; beautiful description) and got it back in and started up again.. But stayed a bit lean. Drove good and all, just cruise was more or so 18-20. Under wot was 11-12. I haven't been able to check fully as I am working and could not fully troubleshoot nor check codes.

    I have Nistune, 3in turbo back, wideband and gauge, intercooler and a cone filter. I will smoke test it tomorrow in the morning for vacuum leaks to get that out of the way. If anyone has a general direction that I could be pointed towards would be appreciated.
  • #2
    Sound like fuel … injectors ? fuel filter ?
  • #3
    Originally posted by dbruce View Post
    Sound like fuel … injectors ? fuel filter ?
    I'll check the injectors and harness and see if it could be those. I'll test the filter out as well but don't really know a good way outside of checking fuel pressure.
  • #4
    If you're on Nistune just check and make sure that you're running the tune you think you're running (ask me how I know this lol.) You could also run a live logging session with nistune and see if you're getting non-sane MAF readings (got a spare MAF around?) or something. Nistune logs make troubleshooting much easier. Do you have a stock O2 on it as well?

    For what a fuel filter costs just throw in a new one
  • #5
    Originally posted by FrozenZ View Post
    If you're on Nistune just check and make sure that you're running the tune you think you're running (ask me how I know this lol.) You could also run a live logging session with nistune and see if you're getting non-sane MAF readings (got a spare MAF around?) or something. Nistune logs make troubleshooting much easier. Do you have a stock O2 on it as well?

    For what a fuel filter costs just throw in a new one
    I probably will check. Through nistune and see what it gives me, I don't really know too much about the software nor much time to explore the possibilities as I only have access to the trial currently.

    No spare maf nor stock O2 for me.

    i did disconnect the afm and it went straight to 9.x afr. I also smoke tested this morning and found the screw for the idle seeped out. There a way to remove this to see or do I looo in another direction?

    Comment

    • JLaraZ31
      #5.2
      JLaraZ31 commented
      07-02-2018, 04:21 PM
      I'm using a small smoke machine that I hook up to one of my vacuum hose on the manifold
    • Dunkine
      #5.3
      Dunkine commented
      07-02-2018, 08:26 PM
      Like this? http://a.co/10CxVNk
    • JLaraZ31
      #5.4
      JLaraZ31 commented
      07-02-2018, 08:40 PM
      Kind of like that yeah
  • #6
    If you actually have a Nistuned ECU and you're not sure what's running on there, you should really sort that out before troubleshooting anything else.

    By "screw for the idle," you mean the IACV on the side of the manifold?
  • #7
    Originally posted by FrozenZ View Post
    If you actually have a Nistuned ECU and you're not sure what's running on there, you should really sort that out before troubleshooting anything else.

    By "screw for the idle," you mean the IACV on the side of the manifold?
    I'll be sure to look into that after work and see.

    Yes that thing, sorry I tend to some of the names but know what they do.
  • #8
    Yah, sorry, should have put a few more words there - remember that Nistune is controlling your air and fuel, so it's possible that if Nistune's not set up correctly you may not have a mechanical problem. Best to check that first!
  • #9
    Originally posted by FrozenZ View Post
    Yah, sorry, should have put a few more words there - remember that Nistune is controlling your air and fuel, so it's possible that if Nistune's not set up correctly you may not have a mechanical problem. Best to check that first!
    I have another ecu I can test out and see if it changes and go from there.

    It's weird as I've never had an issue before until that happened.
  • #10
    So I tried driving with my other ecu it ran the same way, 18 on cruise, drop when letting off throttle, and back up to lean. I also should have mentioned after I get to 3k rpm it will richen up to 16-14 and can go down to 11. Read codes but where only idle switch and ac.
  • #11
    Short update, struggled to get to the gas statiom to pump so I disconnected the afm and ran at a consistent 10 in idle. And high woild be at 13.5 during acceleration to 2k but at steady speed at a 10. Thoughts?
  • #12
    Short update, struggled to get to the gas statiom to pump so I disconnected the afm and ran at a consistent 10 in idle. And high woild be at 13.5 during acceleration to 2k but at steady speed at a 10. Thoughts?
  • #13
    Another update: I compression tested and have found cylinder 2 has very low compression, almost none. The others where at 120. My best guess could be valves but I know there may be something else that could be involved.
  • #14
    welp considering that's the one that had the mashed spark plug, you should probably not be worrying too much about your AFRs and more about pulling the motor. allegedly you can pull the head with the motor in the car but chances are the motor's coming out anyway so may as well just start with that.
  • #15
    Originally posted by FrozenZ View Post
    welp considering that's the one that had the mashed spark plug, you should probably not be worrying too much about your AFRs and more about pulling the motor. allegedly you can pull the head with the motor in the car but chances are the motor's coming out anyway so may as well just start with that.
    I figured as much, if anything I could also see about doing the vg33 swap but have heard it is a bit of a tedious job
    Last edited by JLaraZ31; 07-03-2018, 06:18 PM.

    Comment

    • Dunkine
      #15.1
      Dunkine commented
      07-04-2018, 09:34 AM
      And not really worth it for the tiny displacement increase if your vg30 is fixable. VG33 heads would be nice, but if you just have a bent valve, I'd just fix that.
      Did you do a leak down test yet?
    • JLaraZ31
      #15.2
      JLaraZ31 commented
      07-04-2018, 10:22 AM
      A leak down I have not, the thought didn't come to mind but I will try that out soon.

      I'll take your word on that mate.