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Thread: 91 vette idle surge

  1. #1
    Electronic Ignition!
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    91 vette idle surge

    Ive been trying to tune this car and have learned alot. but ive charnged the injectors. to 30lb sieman deka. edelbrock heads and superram cam around 520 lift. ive been tunning the ve tables with logging and history tables. but the idle sucks most of the time surging from 800-1500rpm. after idling for some time it will find the stable 850 rpm. im seeing the map fluctuate. spark fluctuate and pulse width fluctuate. oh and blms. please help. piont me in a direction. right now im spinning in circles not sure what to loock at.
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  2. #2
    Fuel Injected! 84Elky's Avatar
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    If you can post a log file from TunerPro I'll try to help. Either post an .xdl log and your XDF file, or an exported .csv file.
    Thanks

  3. #3
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    scalars experimental spark angle set to 90 degrees

    i dont know what this is or what it should be.
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  4. #4
    Fuel Injected! 84Elky's Avatar
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    Quote Originally Posted by dbstainbrook View Post
    i dont know what this is or what it should be.
    Please be more specific as to what not understood.

    Since your are running $8d, I exported your log using the S_AUJP XDF (attached). That will cause some things your BIN does not have to be reported incorrectly, but not a issue for basic stuff. Also moved PE, CL samples, etc. to separate tabs so could properly analyze the log while running in CL.

    Please take time to review the attached exported log and analyzer data. It tells you everything that is going on with your car. Several things OK, some not OK and must be corrected.
    • Look a log file:
      Have VSS Err 24. Not critical, but likely a bad connection somewhere
      Have Err 42-CORRECTED-Could be either EST voltage on bypass line at <= 300 RPM or NO voltage > 300 RPM (most likely). This is critical and will affect many other things. Look at SA-REF and SA-TDC. Both are the same. REF should be 10 deg < TDc based on your Base Distributor setting. Something not right with ICM, pickup coil, bypass wire, wiring connections, etc. I would not drive this car unti this is fixed. You are sending 40 degrees to the ECM to run the engine. NOT GOOD! (see knocks below)

    • Look at analyzer:
      Voltage good
      o2 sensor data good
      Coolant/MAT OK
      Injector BPW OK
      BLMs all over the place. Some odd, some even numbers. That cannot occur. Code forces all to be either even or odd numbers. Could be due to Err 42.
      Irrespective of that issue, some way rich and some way lean. The analyzer "BLM VE CORRECTION" Tab shows exactly where.
      Idle MAP a problem. Way too much variation. Could be due to cam, but doubt it. MAP sensor may be the issue but has characteristics of a vacuum leak. But please post your exact (ALL) cam specs
      SA-TDC seems way too high, even if Aluminum heads.
      Err 42 is causing many knocks and retard even under mild load
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    Last edited by 84Elky; 3 Days Ago at 09:32 PM. Reason: EST Correction

  5. #5
    Electronic Ignition!
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    today i changed the spark table and icm cleared codes set spark angle to 45. and whilie driving the timing seems high 20sto low 30s. when i am stopped it goes right back to 45-47. what items affect this just at idle. i dont have the cam specs i didnt build this engine. it does have edelbrock rpm heads and superram intake. i took valve cover off and measured the lift at pushrod and multiplied to get a close number on lift. aside from timing changes i adjusted the ve table with your analyzer. i have a new log fill but dont know how to export and enter into the analyzer.
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  6. #6
    Fuel Injected! 84Elky's Avatar
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    Quote Originally Posted by dbstainbrook View Post
    today i changed the spark table and icm cleared codes set spark angle to 45. and whilie driving the timing seems high 20sto low 30s. when i am stopped it goes right back to 45-47. what items affect this just at idle. i dont have the cam specs i didnt build this engine. it does have edelbrock rpm heads and superram intake. i took valve cover off and measured the lift at pushrod and multiplied to get a close number on lift. aside from timing changes i adjusted the ve table with your analyzer. i have a new log fill but dont know how to export and enter into the analyzer.
    Two things:
    1) What exactly do you mean by "set spark angle to 45"
    2) Look at your spark values in 2.xdl. You could also see these things if you exported the xdl log to a csv (TunerPro: Acquisition>Export Log File and follow directions to get a .csv file for Excel). SA-REF = what the ECM sees to run the engine is hosed. You should not be running this engine until that is fixed. Some component is failing or is not wired correctly. I'm surprised it's running. Nothing can be analyzed/determined until you see SA-REF being approx. 10 degrees (your base Dist setting) less than SA-TDC.
    2 Spark.GIF

  7. #7
    Electronic Ignition!
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    in the scalars the last one says EXPERIMENTAL spark angle. it was 90 degrees. i changed it to 45.

  8. #8
    Fuel Injected! 84Elky's Avatar
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    Quote Originally Posted by dbstainbrook View Post
    in the scalars the last one says EXPERIMENTAL spark angle. it was 90 degrees. i changed it to 45.
    Can you please post the XDF you're using? I know $8d code inside and out and have no idea what that is.
    Tks!

  9. #9
    Electronic Ignition!
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    here it is. thank you for all your help.
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  10. #10
    Electronic Ignition!
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    whoops here wego
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  11. #11
    Fuel Injected! 84Elky's Avatar
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    In all my years of doing this, I've never seen that XDF or that Scalar text (EXPERIMENTAL spark angle). Whoever developed this XDF did not know what they were doing or they were using if for an engine that had a Distributorless Ignition System (DIS). The parameter at the address of that Scalar (0x28) is the Maximum Retard allowed for a distributor 8 cylinder engine and SHOULD NEVER BE CHANGED!!!!!. That's why it's not in any valid XDF except for S_AUJP.

    First thing you MUST DO is to correct your BIN to get this value back to -3.87 degrees max retard:
    -Using your weird XDF, change the value back to 90 and save it
    -Select the Hex Editor icon in the TunerPro banner
    -You should see at address 0x28 and 0x29: FF F5
    -If that's not what's there, change it to FF F5
    -Save the BIN

    Next, dump your XDF and only use the attached. You can now make changes to the BIN with confidence. This is the XDF that can be downloaded from tunerpro.net, modified to edit some additional items as described in the attached documentation.


    Not to complicate things, but when you get the spark straightened out, you need to upgrade to S_AUJP v6. Very easy to do and can tune/change/report virtually everything.
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  12. #12
    Electronic Ignition!
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    how do i do this upgrade to s-aujp v6.

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