lean fuel trims but does not set code…yet

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  • #262199
    mgrover
    Participant

      So as above, its a Range Rover Sport 4.2 SC. The story is a long one but I’ll try to keep to the important bits.

      Bought above car. It had codes, lean and fuel trim codes. It had an lpg system, took it to a man who knew all about it and boom he says the valve seats are tanked due to LPG. Basically all heads rebuilt, new seats, new valves, new timing chains the lot.

      Except after I got the car back the codes reappeared, turns out they only went away because he reset the adaptations so after 50 miles or so codes again.

      So I take it to the dealer to get a PCM update, and the fuel trim codes go away. But the lean codes stay. Okay so we’re getting closer.

      I replace the PCV with a oem replacement. No Change.

      Replace all 4 02 sensors. Ran several petrol cleaners through the system and had the fuel pump replaced. Still not fixed.

      I look a harder look at the MAF, turns out it wasn’t an Denso OEM unit. So I put in a Denso unit and the lean codes went away. But I still currently high fuel trims.

      I’ve smoke tested the shit out of this engine and haven’t found any obvious leaks. The trims below seem to indicate maybe dirty injectors? My theory is there gunked up (130k of usage) and when opening partially they spit instead of spray but under full load they are fully open and its not as much of an issue?

      fuel trims

      The sub feedback trims are all zero.

      But removing injectors on this car is a involved process which means I’d have to remove the intake/supercharger etc etc so I wanted to be sure before I did it.

      Cheers

      #262207
      mgrover
      Participant

        oh also when i drive around i get random misfires but never enough to set a code. i did notice when am cruising at 70mph, the knock sensor would go off, but it has to be for an extended period of time. it goes off on bank 1, then i get cat efficiency codes on both banks.

        #262692
        Naughty Nate
        Participant

          What are the fuel trim values at idle? Do they change when pressing the gas peddle?

          #262741
          mgrover
          Participant

            yes they do but thats because its a different load/rev range. the table above shows the different levels

            #264258
            Naughty Nate
            Participant

              Do the fuel trim values increase or decrease when giving it gas?

              #273864
              mgrover
              Participant

                they decrease it seems

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