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  • 1g no boost

    hey all my 1g is not going past atmoshperic/equalised pressure, as in it compresses enough air to take it off vacuum. but not enough to go past ~1psi

    this happened out of the blue after driving it to work one morning- it was wet that day.

    no engine light on. (it does work)
    no black or white smoke. nothing when driving even when under conditions that would generally create boost.
    the wastegates arent stuck open (tested them with compressed air they open so are obviously.. not open at all times.)
    no piping/hoses appears to be off, and no sounds of boost leaking.
    ran vehicle with boost t detached, as in turbos would not gate.. no different
    car drives around normally but without boost.. so a
    NA 1g
    it has fuel. fuel filter will be changed as its atleast 2 years old but it would restrict it at higher rpms and not be so suddenly and so consistently giving me this problem.
    pump seems ok as car drives around fine. unless it is not providing enough pressure and turbo pressure is preventing fuel from injecting?

    three codes where present after swapping with another AFM (which was broken anyway) they are : 24 31 32
    they relate to (24)air intake thermo sensor , (32)afm open circuit and (31) one on idle. - these have not been cleared so probably from starting with dodgy AFM.

    as the turbos barely make any noise, the pressure stops at an equalised pressure/vac, the car drives fine. my thoughts are this :

    1)dodgy AFM. will have to clear codes (unplug ECU?) and check again.
    WTB AFM in good nick btw

    2) ECU. will be checked when un-plugging ecu

    3) the ECU is de-rating the engine as a result of codes... but ive accidently left my AFM unplugged and once plugged in its fine.

    anyway thanks for checking this out and I hope this helps someone out with the same problem one day.

  • #2
    after looking through wiring diagrams there appears to be a fuel pump control relay, apart of the surprise surprise EFI circut( as is AFM) with a circuit providing 12 volts, and another circuit with a resistor. perhaps this is for de-rated/limp mode. perhaps caused by afm.

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    • #3
      if someone with awesome wiring diagram knowledge can help me that would be awesome. i got this shit but i have no idea how the 'circuit opening relay' works. its like a relay with a mini relay powered by itself in the middle of the switch and power side. wtf?

      http://www.supra.co.nz/1g.htm

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      • #4
        Circuit opening relay gives power to the fuel pump and is triggered by the ECU.
        .
        - Complete English z20 Wiring Diagrams
        - All Circuits
        - Every Connector
        - Completely in English.

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        • #5
          yeah i was looking over it and those diagrams look a bit mismatched.
          any ideas Z2TT?

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          • #6
            Those symptoms are what mine had when the turbo died (exhaust wheel came off, 1jz twins). The car still ran fine but it wasn't making any boost.
            Soarer Motorkhana
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            • #7
              check both your knock sensors are plugged in correctly, if one is disconnected or not working the ecu will go into limp mode and will run like yours is.
              1989 JZZ20 Soarer 1JZGTE, The Project.
              1992 LN106 Hilux 4x4 5L, The Daily

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              • #8
                sounds like a good idea, if only it wasnt pissing down rain, would it throw a code? i have a constant flashing eng light.

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                • #9
                  it could be turbos then, they make very little sound now. but unless both of them went at the same time?

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                  • #10
                    Mine was just one but still had that effect.
                    Soarer Motorkhana
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                    • #11
                      Faulty knock sensors won't usually throw a code so it might be worth replacing them from a known good engine or getting new ones. The turbos are probably not making noise as they were before because they are not making boost like they were before.

                      I haven't heard of it happening much with 1G-GTE than with 1JZ-GTE, but maybe you can remove your cat and see if you have any debris in there from the turbos.

                      You might want to check for Error codes since you have a constantly flashing engine light.
                      .
                      - Complete English z20 Wiring Diagrams
                      - All Circuits
                      - Every Connector
                      - Completely in English.

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                      • #12
                        sorry i ment to say the constantly flashing engine light is when i bridge TE1 and E1 checking flash codes, after clearing 24 31 and 32 relating to AFM. cat is a possibility, there is so much blue flange goo from the exhaust mob hanging off the dump flange. but it was fine one morning, not fine in the afternoon, and the flange is after the cat! ill take the knock sensors off my original 1G and put them on, and if i have the car in the air i will check for continuity from to the ECU to the if the wiring diagram i linked earlier is correct. rusty exhaust studs and nuts that love to snap and damage threads, not my favourite past time haha

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                        • #13
                          Does it run the entire rev range? Is there any flat spots?

                          Got the AFM here and two sets of fuel relays which I have now by-passed. If you are interested.

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                          • #14
                            man ive not taken it above 4 grand because it just doesnt feel healthy. if it didnt go higher would i be looking at an AFM problem?

                            I checked from the knock sensor plugs to the ECU, .5 ohms each
                            I replaced knock sensors, the ones on there where toyota-denso, they were only just tighter than hand tight?, and the ones I put in off my original 1G where not toyota. and there was no difference. not knock sensors.

                            when i go flat foot, the turbo light comes on, but guage still reads ~0 and no boost is felt.

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                            • #15
                              Fuel Pressure Regulator, Fuel System.
                              .
                              - Complete English z20 Wiring Diagrams
                              - All Circuits
                              - Every Connector
                              - Completely in English.

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