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Thread: Help with tune adjustments

  1. #1
    Junior Member SuperChevy's Avatar
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    Default Help with tune adjustments

    I have recently upgraded the computer on my 97 K3500 to a 411 PCM. I installed a custom os and copied the calibrations from the system loaded on the PCM when I bought it (express van). The truck idles good but stabbing the throttle causes the engine to bobble really bad. If I keep it under 1/4 throttle the engine revs up without bobble. At WOT it bobbles for a second then runs strong- anything less than full throttle results in a continuous bobble almost stalls completely.
    I am hoping to get some insight on which parameters are out of line- see attached tune and log.

    Some info on the truck:
    97 7.4L Engine
    Ported heads
    28lbs injectors
    whipple super charger- old school with two addition 50lbs injectors at the throttle body
    Granatelli MAF
    Gibson Headers
    High Flow cats
    4:56 gears with 35" tires


    Any help pointing me in the right direction would be greatly appreciated since I am new to self tuning.
    Attached Files Attached Files

  2. #2
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    Get rid of the Whippletronics it will continue to be a nightmare.
    Check out this file.

    -Justin
    Justin@EFIMuscle.com
    Attached Files Attached Files

  3. #3
    Junior Member SuperChevy's Avatar
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    L31Sleeper,
    Good call on the whippletronics.

    I cut them out of the loop and truck runs like a striped a$$ ape again. I appreciate your input and help. I loaded your changes to my calibration as well and seems to work good- the truck has been sitting for 4 months so I need to go spend a couple days salary and fill the tank with some fresh gas (predetinating under load right now) but I can at least have confidence that I can now go farther than a block from the house with the new PCM and tune.

    Thanks again
    Garrett

  4. #4
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    Do you have a 2 bar MAP sensor ?? Your tune is not setup for one.
    If you have one I could simply change the tune, If not you will need one.

    -Justin

  5. #5
    Junior Member SuperChevy's Avatar
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    I changed the MAP to one from a Cobalt which I thought was a 2bar sensor but when I scaled the MAP at 190 the tuck would not start unless the throttle was at 50%. Right now it shows 4.8v and 15 lbs with the scaler at 94- I dont know enough about the sensor to know if thats indicative of a 1 or 2 BAR sensor.
    G

  6. #6
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    That is a 2 bar sensor for sure, What is the MAP reading a 15lbs it should be between
    200 and 210 KPA. I would try going back to 190.

    -Justin

  7. #7
    Junior Member SuperChevy's Avatar
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    At key on engine not running the readings on the pid are as below.
    GM.MAP =4.8v and GM.MAPBOOST_DMA =15.2lbs
    The dashboard says it reads the MAPBOOST PID as kpa but the data tab shows that sensor as psi. I will upload the calibration with the scaler turned up again to see what happens now that the whipple computer is not in the system
    Thanks
    Garrett

  8. #8
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    Quote Originally Posted by SuperChevy View Post
    At key on engine not running the readings on the pid are as below.
    GM.MAP =4.8v and GM.MAPBOOST_DMA =15.2lbs
    The dashboard says it reads the MAPBOOST PID as kpa but the data tab shows that sensor as psi. I will upload the calibration with the scaler turned up again to see what happens now that the whipple computer is not in the system
    Thanks
    Garrett
    HA Ha.......well if you are making boost with the engine not running I wanna know your secret !!

  9. #9
    Junior Member SuperChevy's Avatar
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    So maybe I misread the data- the MAP boost pressure read the same as the BARO with key on- I assumed it was reflecting atmospheric pressure as I am in the 714 and close to sea level. I loaded the tune with the MAP scaler at 190 and the truck runs but idle is very rough. However after the flash my scan tool is not scanning anymore it has started giving an error of "no response from vehicle" when I push the yellow button to start monitoring. The learning curve continues.....Ill work out the scan issue and work on the idle but at least its running better now that the whipple stuff is out of the way.

  10. #10
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    Now that it's set to 190 how does it run under power ??
    Do you have a Wide Band O2 ??

    -Justin

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