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  • over fueling problem

    hi everyone i have a 1995 r33 gtst, only things done are an apexi filter, full 3'' turbo back (no cat), and a fmic, hks blow-off..... so car idles fine and cruises ok but once you start pushing on the gas pedal my afr's (its a narrow band) just start droppping, to as low as 10 to 1 and as soon as i hit 5 psi i hit fuel cut. So my buddy has nistune and we plugged his laptop into my car and watch what its doing and everything looks normal expect for my maf and injector which under any kind of load max out, so we thought the maf was defective and i sourced a compatible maf and install it.... no different, try removing the blow-off and installed the factory one..... no difference, checked all the piping for leaks.... all is tight and no leaks at present time.... has anyone one had this problem or something similar? the motor is a r33 series 2 motor.

  • #2
    is it holding boost?
    Proud owner of the 2nd Skyline and the only GTR on the island!

    Boost@14PSI, YellowJacket Coils, Extreme TSC, Full Nismo N1 Bodykit, Greddy Speed Cut Controller, HKS Turbo Timer, 280LPH Denso Fuel Pump, Nismo Slave Cylinder, AMS BOVs, Nismo Clutch Pivot, ACT Xtreme 6 Puck and HDPP, Greddy Panel Filter

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    • #3
      it climbs to 5 psi then fuel cuts obviously boost drops due to fuel cut but then builds to 5 psi and repeats

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      • #4
        how could you know it drops to 10 with a narrow band sensor? 14.7±1
        fuel cut with the stock ECU map happens when you MAF return more than a given voltage~4.1V if I remember. Nistune should give you the maf voltage.
        if two indentical RB25 MAF give the same voltage, it really means the car is ingesting a large amount of air. but at 5psi.. it souldn't happen, unless you have a big turbo
        I would recommend to have your car checked out with a decent wideband and get the advice from a reliable tuner in your area...
        Marc-André
        _________
        2.2L RB20 GTS-T
        ECU modification enabled - PM me for details

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        • #5
          Some call it load cut / boost cut.

          It sounds like stock ECU could be switching to knock maps, which could affect the way TP (formula includes input from MAF) behaves and would explain the drop in boost level, injectors maxing out, as they do on knock fuel map. Check condition of knock sensor or for anything loose on engine that knock sensor can pickup as excessive engine noise. Even check sparkplugs, as wrong heatrange, gap (missing) could set knock sensor off. The fuelcut could be the safety revlimiter at 5000rpm (on RB20DET, might be set different on RB25DET), which I think can engage when knock sensor, wiring, etc is faulty.
          Last edited by Skym; 08-08-2010, 06:14 AM.
          RESPONSE MONSTER

          The most epic signature ever "epic".

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          • #6
            i had my car hooked up to my buddies nistune looked at what was going on..... he send we a screen shot......

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            • #7
              bumps

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              • #8
                so a small update, i dont have alot of time to work on the car, havent try a boost leak tester yet, but i looking at the afm wiring so i disconnected the wiring at the afm and at the ecu, and checked resistance on the wires. pin 2 on the afm (5v reference i'm guessing) has .6 ohms on it and pin 3 (guessing reference) has 1.3 ohms on it. so im going to try cutting out the wires and running new ones

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