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Thread: MAF only tune car wont run...

  1. #1

    MAF only tune car wont run...

    Looking for some help. TCCS07 has been helping but maybe the masses of minds together can help.

    2008 cobalt LT 2.2 engine/trans/harness/etc. Added ZZP S/C kit with 4 bar MAP.

    Have been running VVE tune fine. Car starts are runs as expected, still working through perfecting trims. If i take the VVE file and only change the MAF fail freq and dynamic airflow to low RPMS. After sitting for a long period of time car will start and idle for a few seconds (see attached VVE5 log). Once it dies and you attempt to start it, it will immediately kill when attempting startup at a few hundred RPMs.

    Ideas?

    MAF.hpt

    vve5-1.hpl

  2. #2
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    your ecm does have a scale for iat2 temp i forgot. i was thinking of my ecm the p12 like a dummy but even so your iat2 stays 32 no matter what but again your ecm doesnt have any pins for iat2. im going to send you those pin locations in a few min but ill post here to. what happens if you if you run the blend tune like factory does? where it uses both vve and maf for fueling. does it still die out? because at least we established vve only is good and runs so its not a idle airflow issue causing the dying out at least i wouldn't think because base running airflow is base running airflow no matter what. try the blend tune setup and see if it stalls out like that still because if so id say something is going on with the maf circuit and ecm. if it does stall out see if it does again with the tb vac line disconnected again which i found odd that it did because that makes it seems like it doesn't have enough air because inducing a vac leak does just that
    Last edited by TCSS07; 04-07-2019 at 05:26 PM.

  3. #3
    I will try the blend tune tomorrow to see if that runs.

  4. #4
    Senior Tuner cobaltssoverbooster's Avatar
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    iat 2 is map sensor internal depending on models. check map sensor to verify 4 wire harness
    2000 Ford Mustang - Top Sportsman

  5. #5
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    Yeah I told him that before but the 4 bar hes using only in a 4.pin map. It doesn't have a iat2 reference and his ecm doesnt have a pin out for it either which I found weird because the vehicle should always have a iat2 reading right?

  6. #6
    Senior Tuner cobaltssoverbooster's Avatar
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    if the oem harness for the map sesnro has 4 pins then it has a built in iat which functions as iat2. in order to make it work another sensor that is 4 wire must be used of he has to add an external iat sensor and wire the signal from that into the map harness.
    2000 Ford Mustang - Top Sportsman

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    True, he said the ecm was from a 08 cobalt l61 and harness as well so I looked up the map connector and only calls out a 3 pin and ecm doesnt have a iat2 circuit so he will just have to add a seperate sensor but could you piggy back off the iat1 circuit or would that mess up the readings

  8. #8
    Just a heads up i was able to cancel the LSJ map connector but not the 4 pin 2.5Bar LSJ MAP sensor (with IAT2) so that will be here in a couple days. I am more than willing to trying wiring it in with a strategy

    It we find out the IAT is the issue and the ECM is the limiter i will get a new one if i dont have to rewire all the ECM plugs....

  9. #9
    Senior Tuner cobaltssoverbooster's Avatar
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    i dont have access to any ecu wiring diagrams so i dont have the ability to track down pin connections to match with features.
    2000 Ford Mustang - Top Sportsman

  10. #10
    Bingo... no can run with MAF installed for VE/MAF setup.

  11. #11
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    it will or will not run in blend?

  12. #12
    Same as with MAF connected in MAF only. It runs for a few seconds (longer today because it sat) then it dies. I ohm'd out the pins (thanks!) to the ECM. All fine. So I dont understand ground vs. low reference. Pins B and D are shorted to ground and to each other (obviously). And D is a dead short to X2-42. Should that be that way? I read low reference should have some resistance to ground? I could have easily bundled the wire off X2-42 to the main harness ground when combining.....

  13. #13
    If need be i can tap into the D pin on the MAF connected and bypass the current signal wire to X2-42. Cut at the X2 connected and tap in there....

  14. #14
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    pin d gets grounded by the ecm and pin b is a chassis ground usually shared among other systems

  15. #15
    Yeah, so like i thought. Im sure i mixed them together when combining harnesses. Not sure how to break them back apart. Heck some of the guys with these kit cars just tied every ground together to get them running when combining harnesses. Now i know the problem.

  16. #16
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    well if you know you messed it up at the maf connector you only need to either switch the pins around for b and d or just cut and splice them to how they should be but if you dont know for sure where like at the ecm or the maf youll have to just re do the 2 wires on that circuit

  17. #17
    well theres no way its all getting re-wired. I will try a couple things and see if i can get it separated. Thanks for the help TC

  18. #18
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    no i meant just the 2 wires in question. find the wires at the ecm connector,cut/splice but leave yourself enough wire and do the same at the maf connector and just run 2 new wires real quick to see if it fixes it
    Last edited by TCSS07; 04-09-2019 at 07:37 PM.

  19. #19
    workin it already. thats what i was thinking...

    Already verified the ECM low reference pin is not shorted to ground.

  20. #20
    So no go on that route. But i said F it and decided on a "floating reference"???

    Just cut the D line all together and connected it to nothing. Ran fine. Loaded MAF only tune... car runs....