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LS1 Torana

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    Fuel pressure is good at all times (I have a fuel pressure logged wen driving).
    Next thing to check is the purge valve. Could be playing up when told to purge and too much unmetered air is finding its way in?
    Will remove the purge hose to the charcoal cannister and plug the purge valve and see what happens on the next drive.


      What do your fuel trims do bank to bank? I bet you have the 02s backwards


        02 voltages and fuel trims are decent most of the time (I did swap them around and check they were on the correct banks)
        Its not a bank to bank issue. When the issue presents, both 02 voltages drop in a massive way (approx 40mV). It cold starts and idles well. Feels pretty strong when crusing and when giving it a push. 02 voltages and trims look as they should during this time (02 voltages oscilating from approx 0.2v to 0.9v)
        Fuel trims are not opposing each other from bank to bank.
        I did have an exhaust leak at the collector when first getting it running that caused a drama on one of the banks (adding a heap of fuel as it thought it was rich). But this was obvious, presented at all times and is sorted now.

        I think ive crossed off the issue being fuel related, and it seems to have plenty of spark on each cylinder. That only leaves and air issue (in my simplistic view!). The only items that vary the amount of air intake past the MAF are the the idle air controller, throttle blade and purge valve.

        Other checks: MAF frequency data doesnt do anything strange when the issue presents suggesting the MAF and MAF wiring is ok. The IAC seems to work ok as I can force it to a setpoint and the engine responds as it should. MAP sensor values look like they should, timing looks as it should, commanded AFR looks ok also. Im running out of things to check!
        The vacuum lines are new and have been checked multiple times. I also just ordered a new intake tube incase the used factory tube has a crack that i havent found. Its really pissing me off.


          Update: Seem to have this sorted.
          Ran the car in Speed Density mode and it seems like its fixed. Touched up the tune using the fuel trims and it feels pretty good.
          The data from the MAF channels look good (frequency, calibration etc), but for what ever reason it seems to do something weird every now and then. MAF less from now on it is!


            Well done Shaun. Enjoy it and lump on some kms