85T Bad Hesitation/Hiccup/Misfire

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  • #16
    Originally posted by Z_Karma View Post
    Also could be ECU related.
    My 84T runs fantastic, no problems, passes emissions and is reliable.

    However, if i try to drive off on a cold start without letting it idle for a minute or so, it'll buck and stutter and maybe backfire if i don't let off or feather the pedal.
    The earlier ECU's had a problem with lean surge when they're cold. IIRC, there was a known issue and a second module was added into the harness and mounted
    beneath the battery tray, although i cannot find the TSB that mentions this. Mine has this module and still has issues with cold starts.

    There was also an oldschool fix by switching the CHTS signal to the FTS

    Some info is still archived in various forum threads like this but a lot is not easy to find anymore.

    Over the years on here and other forums, I've pretty much surmised that the best remedy for this cold start/lean surge issue is to convert what is required to run a later model ECU.

    This may or may not be related to what issues you are encountering but it could be related.
    I appreciate that, what year do you recommend? 87 88?

    Also checked my codes and have 21 and 31. Confusing me how they came up.
  • #17
    Quick update: Today after work it started acting up again even at operating temps and would struggle to accelerate. But as I was arriving home it acted just fine. Could the codes have something to do with this or could it be something else? afm?

    acted perfectly normal today with only a sputter once in 4th. Although I did find a two wires touching those from the CAS on the passenger side head and moved them out of the way. Maybe that caused something? Beats me.
    Last edited by JLaraZ31; 08-31-2017, 07:18 AM.
  • #18
    Intermittent issues of any sort are a pain in the ass to troubleshoot, but you do learn a lot. You should find out what those wires are in the diagram (GOT FSM).

    As far as recommended ECU, Read here.

    Xenons site has tons of great information.


    84 AE/Shiro #683/Shiro #820/84 Turbo
  • #19
    Originally posted by Z_Karma View Post
    Intermittent issues of any sort are a pain in the ass to troubleshoot, but you do learn a lot. You should find out what those wires are in the diagram (GOT FSM).

    As far as recommended ECU, Read here.

    Xenons site has tons of great information.
    Yes, I do have the FSM as well as a Haynes manual (haven't sat down to look at both for the differences). I looked up to what stray wires went and they were for the air regulator. Still in the engine just not hooked up.

    I appreciate that very much, because of school I'm not going to have as much time with it but I will do what i can to keep updated on.
  • #20
    So I went and bought a multimeter and tested my chts (both my spare and current one) and both are working fine. Because of my code 21 I am going to test the transistor and CAS to be safe. Is the prw2 a pnp or npn? Anything else i should test for?
  • #21
    So, folowing the FSM and everything you guys have told me to check I am stumped. O2 is good, ignition coil is good, CAS is good, transistor only differs by almost 1 volt, and afm is good. Checked my plugs and they're black and smell of gas. I'm almost out of ideas but will check and see everything else one more time.
  • #22
    Uhhh… hmm. Have you got a fuel pressure tester? Check and make sure your FPR responds to changes in vacuum… you can just pull the vacuum line and that'll tell you if your FPR is doing something, but it would be better to actually check the fuel pressure.
  • #23
    So, Im gonna go ahead and say i have no idea what i did when testing everything, but she runs perfectly, no surges at cold or operating temps, all codes cleared, everything perfect. 1st I thought it was just acting right as it did before the issues, but she's not giving me problems or issues. I guess make sure everything is reading right? I've no idea right now.

    Comment

    • Dunkine
      #23.1
      Dunkine commented
      09-06-2017, 10:02 AM
      Self healed!
  • #24
    So update after a week: it's been running good; however every so often I will get the symptoms again but more controllable than it was before and it's very short. Checked codes and I have AFM, CAS, and Load signal. Any input on these codes? I'll test them when i get out of classes.
  • #25
    So after looking things up thanks to Z_Karma's link I found out my ECU is from an 86 NA. For the 6 months I've had the car it never gave me any issue until this one. would it cause any issues using an NA ecu on a turbo engine not counting my current situation? Should i try a turbo ecu from an 84/5/6/7?

    Comment

    • Dunkine
      #25.1
      Dunkine commented
      09-17-2017, 04:36 PM
      I've always heard turbo motor, turbo ECU, n/a needs n/a ECU. I wonder if the n/a ECU is causing your messed up air/fuel ratio.

      On my Jeep if I throw a set of new plugs in it, it will run fine for a month or so and the Check Engine light will go off, but after that it starts misfiring again and light comes back on, usually when I leave it idling in the driveway or in traffic. Ugh, winter is coming I need to tear into that and get it fixed…bleh, wish it had a nissan engine in it… :P
    • JLaraZ31
      #25.2
      JLaraZ31 commented
      09-18-2017, 07:15 PM
      Thing is it has been running fine with it for several months but this has been very recent. I'm not quite sure what to look at right now as far as if it is alright to use or not.
  • #26
    I keep checking the codes as it will run perfectly fine with no issues and suddenly it will black smoke like a diesel and not want to accelerate, but once it can it will accelerate like there was never an issue until I get within lower RPM ranges. Only codes I have are 13, 21, and 31, after reading the FSM 21 could be from fouled out plugs from how rich it has been running, but 13 still eludes me. I'm assuming that 31 is with 13 as the first time it has acted like this was when I got the car in february and it turned out to be the wire for the CHTS being outside of its pin. I've checked the CHTS and the CHTS subharness as far as readings go and, when disconnected from the ECCS, reads what the CHTS is showing (which is within working range as far as the FSM says), but when connected to the ECCS it reads somewhat lower than what the CHTS does. Is that normal or is my ECU gone? Also I've inspected the CHTS subharness closely and saw that it has some damage to it could this be my issue or would it not matter as much since the proper reading from the CHTS is going to the ECU pinouts?
  • #27
    Stop trying to troubleshoot other things until you put a turbo ECU in the car. The main thing that's wrong is that your injectors are, like, 50 per cent larger than the ECU believes they are and the fuel and timing maps are different.
    Last edited by FrozenZ; 09-19-2017, 01:48 PM.
    • 1 like
  • #28
    Originally posted by FrozenZ View Post
    Stop trying to troubleshoot other things until you put a turbo ECU in the car. The main thing that's wrong is that your injectors are, like, 30 per cent smaller than the ECU believes they are and the fuel and timing maps are different.
    It will be awhile before i can get a turbo ECU for it. Are there pinout differences between the ecus?
  • #29
    Although I'm not sure about the pinout differences, everyone is right about the ecu. NAs came with 180cc injectors while Turbos came with 260cc injectors. The fuel pressure for both are the same, so you have a Non turbo ECU which continues to foul the plugs since the injectors are 80cc bigger than what its programmed for. Rockauto has remanufactured ECUs, but I've never personally ran one. Also here's a website you should get familiar with.

    Rockauto(Parts distributor)
    http://www.rockauto.com/en/catalog/n…computer),2896

    RedZ31(Jason's site that has a ton of information about our cars)
    http://redz31.suomiz.net
    1986 z31 NA2T(Motor is being assembled)
    1984 z31 Turbo 5 speed(slowly being parted out)
  • #30
    Originally posted by GodofRichy View Post
    Although I'm not sure about the pinout differences, everyone is right about the ecu. NAs came with 180cc injectors while Turbos came with 260cc injectors. The fuel pressure for both are the same, so you have a Non turbo ECU which continues to foul the plugs since the injectors are 80cc bigger than what its programmed for. Rockauto has remanufactured ECUs, but I've never personally ran one. Also here's a website you should get familiar with.

    Rockauto(Parts distributor)
    http://www.rockauto.com/en/catalog/n…computer),2896

    RedZ31(Jason's site that has a ton of information about our cars)
    http://redz31.suomiz.net
    Reading into the information about ECUs I saw it mentioned the desirable unit for 84/5 turbo is the 88/9 NA ecu; however wouldn't that still be somewhat similar to the 86NA as far as injector sizes go?

    I appreciate all the helpyou guys are giving me greatly.
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