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Thread: Adjusting Air Fuel mixture '7747 AKDX

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  1. #1
    Fuel Injected!
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    Adjusting Air Fuel mixture '7747 AKDX

    Need assistance in modifying the bin to address the following condition:

    I have a modified '7747 ECM with a 28-pin ZIF socket installed in my '92 4.3L S-10. I burned the attached AKDX.bin file onto a 28-pin EEPROM which is now running in the truck. Yesterday, after running for a few minutes, the engine died and would not restart. While attempting to restart, I noticed a heavy spray of fuel flowing into the throttle and observed liquid fuel collecting on the rear edge of the throttle plates. I opened the throttle wide-open, hit the remote starter button and the engine struggled to restart but did eventually restart. I had to manually control (open and close) the throttle in order to keep the engine running; if I let it go completely the engine would die.

    Because of the heavy fuel spray, on the next restart attempt, I disconnected the driver injector wire and cranked the engine with throttle partially open. The engine started a little easier but continued to ran rough. Once I reconnected the injector wire, the engine struggled again to stay running and I had to manually open and close the throttle in order to keep the engine running. Again, if I let go of the throttle completely, the engine would die.

    Is this flooding condition due to the ECM holding the injector pulses open too long? Can it be adjusted in the .bin? What specifically do I need to do and is the needed adjustment only required in one place within the bin file?

    Thank you in advance.
    Attached Files Attached Files

  2. #2
    Super Moderator dave w's Avatar
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    What Offsets did you use to burn the 28 pin chip? I'm thinking you are using a 27SF512 Chip, which is 64K. The posted ,bin file is only 4K.

    http://support.moates.net/programmin...using-offsets/

    dave w

  3. #3
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    Hi Dave,

    Thank you for looking at my dilemma.

    I believe the offset was what is required for a 4K bin file. I used Flash & Burn with an APU1 to burn the chip. If I remember correctly, I entered the necessary information on chip type and verified the offset and buffer values were correct. Once I completed the burn and installed the chip, I assumed I had done the burn correctly because the engine started and ran. Am I mistaken?

    So, are you saying that if I burned the chip with an incorrect offset that that is causing my problem of too much fuel spray? Or, is the ECM running in limp home mode?

  4. #4
    Super Moderator dave w's Avatar
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    A stock 24 pin chip can be installed into the 28 pin ZIF socket, once the stock chip is removed from the original holder. I would try a stock chip in the 28 pin socket and see if it makes any difference in the way the engine will run. When installing a 24 pin chip into a 28 pin socket, PINS 1,2 27, & 28 are open. It's also possible to install a chip backwards into a 28 pin socket, VERIFY PIN 1.

    If a chip is incorrectly programmed, the engine will run in a limp home mode (too much fuel).

    We are assuming the 28 pin ZIF socket was correctly modified for the EEPROM and correctly installed into the '7747?

    dave w

  5. #5
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    Is the Idle Air Control valve allowing air to be pulled in?
    1994 Chevy G30 Van "Big Blue"
    5.7 TBI, Vortec Heads, Summit Intake, Thorley Short Headers with dual 2.5" exhaust, 4L80E transmission

  6. #6
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    Thanks Dave for the info that I can insert the original 24-pin chip in a 28-pin socket. I did not know that was possible. I just hope I correctly modified the socket and installed it properly without damaging the ECM. Just to ensure I used a correct buffer setting, I will re-burn the chip.

    wanderingturtle, I had installed a new IAC but have no way of knowing air is being pulled in. How do I check that it is functioning properly?

  7. #7
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    Quote Originally Posted by 57 Handyman View Post
    wanderingturtle, I had installed a new IAC but have no way of knowing air is being pulled in. How do I check that it is functioning properly?
    Well, with the air cleaner and throttle body sleeve (part name?) removed, you can put your finger in the IAC passageway hole and feel and listen for if air is sucking by when cranking.
    1994 Chevy G30 Van "Big Blue"
    5.7 TBI, Vortec Heads, Summit Intake, Thorley Short Headers with dual 2.5" exhaust, 4L80E transmission

  8. #8
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    OK...will check that method out tomorrow. Thanks

  9. #9
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    When initially started the engine, Stuck my finger down into that hole and could feel the air bypassing. At the time, we had the key "on" engine "off," the scanner was reading 145 which is the "park" position set in the ECM. At this point, we could have jumpered pin A to pin B on the ALDL and watch the IAC close to 0 on the scanner. 2nd time running, scanner was hovering around 39. I think it's working fine, time to move onto bigger things!!!

  10. #10
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    If you can talk to the ecu it's probably not in limp home mode

  11. #11
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    delco, what do you mean by "talk to the ECM"?

  12. #12
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    Between Kalama Valley runs, managed to install 28 pin zif into ‘747. You’re welcome to try it out. Gonna hafta be around lunch time and only drop off. Gotta go back work!

  13. #13
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    Oh, WOW...guess you did find something to do while your wife was in Hawaii Kai...lol. Rather than you dropping it off, I'll come to you so you don't loose your preferred parking. Plan on going to JBPHH abandoned vehicle auction and swing-by around 1100 or so. Thanks, Stew

  14. #14
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    Normally full limp home mode will stop scan tools and tunerpro from talking to the ecu

  15. #15
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    Thanks Delco,

    So, when you say "full LHM will stop scan tools and tunerpro from talking to the ECU", I shouldn't be able to do any data logging? I was just hooked up to my 7747 via my APU1 and was able to record some data (attached). But I have no idea if these recordings are good as only a few parameters seemed to be responding to throttle changes. Does this level of data logging indicate the ECM is not running in any level of LHM?

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