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Thread: Looking for Help!!! SBC TBI Cant get over 2300 RPM

  1. #1
    Electronic Ignition!
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    Looking for Help!!! SBC TBI Cant get over 2300 RPM

    Hoping a lot more knowledgeable than me can look this file over and see if anything stands out. I am very mechanically inclined but this is my first rebuild with almost zero help other than what i could find on youtube and forums. Please let me know any specific info that could be helpful thanks in advance.

    Background.
    1991 Chevy K5 Blazer SBC 5.7l
    engine was rebuilt and bored .030 over and converted to hydraulic roller
    has new heads from summit
    new distributor
    new temp sensor
    new map sensor
    new alternator
    new plugs
    new plug cables
    new fuel pump - tested ok with rented fuel pressure gauge from parts store - replaced all rubber lines to fuel pump
    new icm - have back up just incase both checked out good at the parts store
    etc...

    The issue i have is when get over a certain RPM is starts to misfire and "bog out" around 2275 rpm

    Wiring has been checked and re checked
    I did pull timing connector to verify timing and i believe that set the code 42 error code or it came on when I hit 2275 rpms not entirely sure. The test I did previous did the same thing as far as bogging out or miss firing but did not throw a code.
    I have fought this issue for a while finally found tuner pro to try to better understand whats going on only im not entirely sure how to read all the data. I can tell that my BLM is low not around the 128 it should be but not sure if thats related to my issue with the bogging down.
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  2. #2
    Super Moderator dave w's Avatar
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    The data log is showing two Errors Code 42 and Low Battery Voltage.

    The Code 42 happened about 2/3 of the way thru the data log. The Low Battery Voltage happened near the end of the data log.

    Attached is a Modified ARJU 91 C-G-K-R-V Truck 5.7TBI 700r4 california.bin with the BPW and SA patches applied. Possibly you have the ability to reprogram the chip with the attached .bin file?

    The BPW and SA patches are very helpful to see what the fuel and spark are doing at the moment Code 42 is set. The low battery voltage might be due the way the computer is wired to battery +, not sure. Low battery voltage is an unusual error to see in a data log.

  3. #3
    Electronic Ignition!
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    Yes, in the thread I mentioned that I unplugged the timing connector to verify base timing was at 0, Im pretty sure thats what thru the ignition control circuit code and the low battery was because I turned the key off before stopping the data log. I will try the bin file you attached and do a another data log and this time I will stop the log before turning the key off. Thanks for the reply.

  4. #4
    Electronic Ignition!
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    Looking at the Bin file you sent I cant see any difference from the one I was using. I believe the Bin file I was using had Spark advance and BPW can you please explain where I can can see the difference. thanks for the help!

  5. #5
    Super Moderator dave w's Avatar
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    Screenshot using TunerPro's difference / compare tool.

    BPW Hack.JPG

  6. #6
    Super Moderator dave w's Avatar
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    Perhaps the screenshot below is helpful too?

    BPW Hack_02.JPG

  7. #7
    Electronic Ignition!
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    Quote Originally Posted by dave w View Post
    Perhaps the screenshot below is helpful too?

    BPW Hack_02.JPG
    lol well now i really feel dumb didnt know there was a "difference tool" thanks for sharing. Ill do another test run/data log and repost. thanks for help!!

  8. #8
    Super Moderator dave w's Avatar
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    With the Patch applied, SA will be in the DataStream. Without the Patch, valuable SA data is missing. Below is a SA sample (4.3 V6).

    TunerPro RT Spark Advance.jpg

  9. #9
    Electronic Ignition!
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    Test with Modifed Bin

    Got it... thanks and sorry Im really new to this software.... my knowledge of what is supposed to be what is extremely limited but you got to start somewhere so thanks again for the help
    I was finally able to do another test with the modified BIN, this time I started the data log before I started the engine, it seemed to run fine until it entered closed loops status and then the INT and BLM start to fluctuate and then it started running rough. Please let me know what you think could be goin on. thanks!
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    Last edited by shawnp707; 11-09-2022 at 05:09 AM.

  10. #10
    Super Moderator dave w's Avatar
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    How are you reprogramming the chip?

  11. #11
    Electronic Ignition!
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    Sorry Im not entirely sure what you mean, I havent reprogrammed anything as far I know. Do I need to reprogram the chip? Are you referring the prom?

  12. #12
    Super Moderator dave w's Avatar
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    Oh, some miscommunications on my part.

    The EPROM will need to be reprogramed with the modified .bin file for the "Patch" to work.

    Perhaps some information about programming the EPROM will be helpful? http://www.gearhead-efi.com/Fuel-Inj...6II-programmer

    The tread is several years old, and some of the EPROM programming options are not available now.

    The 1227747 typically uses a 2732a EPROM. Perhaps the products listed on Amazon (link below) are an option?

    https://www.amazon.com/PRG-109-GQ-4X...2-63e904010ad0

  13. #13
    Fuel Injected!
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    what is fuel pressure? can you test fuel pressure while it is misfiring? I usually get a long line and run it under the windshield wiper or the mirror so it is not in the cab. i would also check with basic stuff like firing order and timing. easy to put a plug wire in the wrong place or crack a spark plug when tightening. I also do not reuse a spark plug if i drop it on the ground....

    ALSO, what cylinder heads did you get from summit? ot sounds like a custom chip will be required.

  14. #14
    Electronic Ignition!
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    Dave, I will purchase both of those items and re write the chip with the modifed bin. I recently found out I was running the incorrect spark plugs and will definitely need a performance chip or to rewrite my current one to match the upgrades to the engine. I was told by the machine shop my upgrades would not affect my ECM clearly they were not correct. Brian for harristuning.com was a big help and quickly determined the issue with my spark plugs and did not seem happy that I was running the factory chip with the modifications to the engine as its for a 180hp engine not a 300hp engine.

    Tayto, I have not checked fuel pressure while driving by key on engine off it was about 13psi. I have checked the firing order several times and rechecked some more, i have not dropped any plugs on the ground but i am running the wrong plugs for the aluminum heads. Which could have potentially hurt them so Im told, Im hoping this is not the case and they were not cheap. I am definitely looking into performance chips do you have any recommendation?

  15. #15
    Super Moderator dave w's Avatar
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    Quote Originally Posted by shawnp707 View Post
    Dave, I will purchase both of those items and re write the chip with the modifed bin.
    I just noticed the power cord for the UV Eraser is not correct for 110 ~ 120 VAC USA, likely 220 ~ 240 VAC for Asia?

    UV Eraser.JPG

    Maybe this UV Eraser: ExGizmo UV EPROM Eraser AC100V-240V Erasable Timer Semiconductor Wafer Erase Radiation for UV Curing - - Amazon.com
    Last edited by dave w; 12-03-2022 at 08:51 PM.

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