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Thread: LSJ issue, the tune or ecm??

  1. #1
    Tuner in Training
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    LSJ issue, the tune or ecm??

    i recently purchased a 2005 Saturn ion redline. long story short im having an issue with the IAT reading weird. first i thought my MAF was bad, well with the mass air flow unplugged it still acts up. the issue im having is when im running the scanner, the IAT will read normal but the little ghost needle that shows your highest IAT will slowly rise. so for instance my IAT will be at 30 degrees, the orange needle will stay around that but the highest needle will go way up past 150*. i even at times have seen the orange needle jump that high for a split second. So i thought ok the wiring is rubbed through maybe.... i cut both wires for the IAT sensor part of the maf 3inches from the computer and it goes to -40 which it should but the highest needle reading will still move up on its own. i even tried putting a spare IAT sensor right at the harness where i cut it to try a different IAT sensor.... same thing. would my ECM be bad??? could the tune casue this? anyone ever see anything like this maybe not even on a LSJ?



    60lbs inj

    2.9 pulley


    long tube header no cat stock exhaust


    ZZP 3in intake

  2. #2
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    newiat.hplcobaltinj2maftune5.hpt


    heres a quick scan but it doesn't show the highest needle on the IAT like i see it when i am actually scanning! weird that it doesn't show it on the saved log...? also posted the tune which is in open loop. (im in the process of trying to tune this damn thing but want to get this IAT fixed first)

  3. #3
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    Codes?
    you need to fix a few things in your tune. the fuel flow rate is all kinds of messed up. it should be a smooth line.
    https://forum.hptuners.com/showthrea...965-LSJ-Guides - read up on some things - i used sjschafer method when i had 60s - worked great - im on 80s now and use the lsj injector spreadsheet data - works great
    theres nothing tune related that will effect the iat reading. those charts are not available to us so thats between the ecm and maf sensor. so if its not reading right you have a problem with either the ecm,maf or wiring. with the maf unplugged it should read -40 which you stated it does so seems the circuit is working
    Last edited by TCSS07; 03-16-2019 at 02:17 PM.

  4. #4
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    Thanks for the reply, ya I tired using a couple different inj data.... this one seems to work the best. And I?m leaning towards there?s something wrong with my Ecm. I literally cut the harness right at the ecm connector and put a spar IAT I had laying around in to rule out the harness and still have that same issue. I?ve really only tuned v8 cars and they have a lot more options in the editor then this computer has.... but even then, I?ve never had an IAT reading like this before.

  5. #5
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    And only codes that came up with for cam crank correlation(I put a new sensor in Bc it wasn?t always starting first hit of the key, but it does now), I did a relearn with the scanner and I haven?t had it come back

  6. #6
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    Well if you change the flow rate it's going to throw off the trims so you'll have to re tune the airflow model accordingly. If you know that iat sensor is good and producing the same results as the maf did then I'd double check the wiring by ohming them out and or bulb check/load test them to make sure the wiring is good and if all checks out then I guess the ecm is screwed up.

  7. #7
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    P0017/P0016 for timing correlation wouldnt mess with the iat calculations

  8. #8
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    Ya I?m leaning towards the ecm is bad. Maybe I?ll see if someone has a computer locally that I can swap in.... only other thing would be the connection at the computer but I have that off when I was ohm out the wires from ecm to maf. Thanks for the replys