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car is jumping from rich to lean to rich...

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  • car is jumping from rich to lean to rich...

    I have an 86T with a stock ECU, 450cc injectors, 4 bar fuel pressure, and a Greddy E-manage controlling it. I have had good luck with the E-manage so far. It is not the E-manage causing the problem.

    I have used this same setup before with NO changes, but for some reason the car toggles between (from what I'm guessing) an open loop mode and a closed loop mode. I have no IAC, TPS, EGR, or O2 sensor for the stock ECU, but I have a wideband to monitor and tune. I can make a hard pull through a gear, but after a shift, it freaks out and runs lean. I have tried an ECU from another turbo car, and it didn't change anything. I swapped ROM chips from a turbo ECU into an NA ECU, and nothing changed.

    Light throttle the car runs very lean. At idle it will either be 12:1-13-1 AFR, but it will switch to open loop and it bogs down a little and gets 15.5-1 or leaner.

    What sensor would make the ECU change maps? Maybe a freak signal telling the ECU the TPS is closed? how can I keep it in closed loop mode all the time? I really need a nistune ECU ASAP. I'm sick of this piggyback.
    86 hardtop shell, 93 SC300 engine, 95 soarer bellhousing, 91 supra transmission, 95 Q45 differential hubs and driver's side axle, 1992 300ZX turbo driver side axle and calipers, 2004 350Z Rotors, 87 300ZX front end/hood, 1999 Viper radiator, 1992 Mustang throttle body. Lots of glue and tape to keep it all together.

  • #2
    have you checked your maf

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    • #3
      StreetFighter wrote:
      What sensor would make the ECU change maps? Maybe a freak signal telling the ECU the TPS is closed?
      TPS or bad connection. If you havent fully checked it then I would.

      StreetFighter wrote:
      how can I keep it in closed loop mode all the time?
      You don't want to do that.

      Overall I would say that you need to check the following. TPS and its wiring. CHTS...as much as I hate to say it because it is thrown out way too much... and the wiring. AFM/MAF and the connection. Vacuum leaks. Stock Idle control items, basically anything that bolts onto the upper plenum.

      If it isnt one of those items you probably have an ECU tuning / E manage issue or who knows.... If none of that help then the best you can do is eliminate all those items the best you can and repost on the thread.
      Just stand back and throw money.
      Performance costs money.
      Reliable performance costs more.

      Comment


      • #4
        Here is the problem...

        I don't have a stock plenum (I have fabricated a sheet metal one) and therefore have no idle controlls.

        I do not have a TPS, or a CHTS. I want to run the car in closed loop mode all the time and fine tune with the piggyback. I had good luck doing that on the last turbo car (116mph trap on bone stock engine with HX35)

        The MAF is fine, but I'll change it with another one just in case (I have a few extras around)

        I just want to have the stock ECU run exactly the same all the time. I don't want it to change.
        86 hardtop shell, 93 SC300 engine, 95 soarer bellhousing, 91 supra transmission, 95 Q45 differential hubs and driver's side axle, 1992 300ZX turbo driver side axle and calipers, 2004 350Z Rotors, 87 300ZX front end/hood, 1999 Viper radiator, 1992 Mustang throttle body. Lots of glue and tape to keep it all together.

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        • #5
          Ah, that makes more sense then.

          Are you pretty sure you dont have an air leak somewhere between the MAF and heads? Shot in the dark but you could be sucking unmetered air into the system???
          Just stand back and throw money.
          Performance costs money.
          Reliable performance costs more.

          Comment


          • #6
            I'll pressure test it today, but I don't think I have a leak.
            86 hardtop shell, 93 SC300 engine, 95 soarer bellhousing, 91 supra transmission, 95 Q45 differential hubs and driver's side axle, 1992 300ZX turbo driver side axle and calipers, 2004 350Z Rotors, 87 300ZX front end/hood, 1999 Viper radiator, 1992 Mustang throttle body. Lots of glue and tape to keep it all together.

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            • #7
              Mine was doing this.

              the chts came unplugged :lol:

              Terrible idea putting those wheels on...

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              • #8
                I think you need a CHTS. The temperature enrichment variable is there in the ecu seperate from what maf voltage input does. I don't think you can voltage correct the maf signal well enough to adjust for the CHTS curve, even if it's an open circuit and the ECU thinks it's disconnected? I don't know, but I would think not. My guess is ttpmin or null adjustment and using a CHTS would at least help correct your problem.

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                • #9
                  There wasn't any air leaks, and hooking up the CHTS seems to have fixed the problem. Thanks Jason.

                  Now the problem is I have maxed out the stock MAF. :cry:
                  86 hardtop shell, 93 SC300 engine, 95 soarer bellhousing, 91 supra transmission, 95 Q45 differential hubs and driver's side axle, 1992 300ZX turbo driver side axle and calipers, 2004 350Z Rotors, 87 300ZX front end/hood, 1999 Viper radiator, 1992 Mustang throttle body. Lots of glue and tape to keep it all together.

                  Comment


                  • #10
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