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Slight misfire thru rpm range

Discussion in 'FAST Support Forum' started by fishhore, Apr 17, 2018.

  1. fishhore

    fishhore Member

    Joined:
    Aug 15, 2014
    car starts and runs great minus the slight misfire I have thru the rpm range. Wot runs fantastic. Have correct plugs and wires for efi and plenty of grounds. Car really does run well just minor drive ability problems like while putting around in 1st gear in parking lots. Only thing I haven’t done yet to remedy problem is switch to a single plane intake. I’m running a rpm air gap with a 1” spacer. I just want to make sure before I spend my time and money to swap that that’s my issue
     
  2. fishhore

    fishhore Member

    Joined:
    Aug 15, 2014
    Also it’s a 383 sbc, aluminum heads, decent little cam, makes 448hp. Already changed map sensor to external, basically just want to know if a dual plane intake +spacer would cause my issue. This issue doesn’t keep me from driving the crap out of it, the slight miss has just always bothered me.
     
  3. fishhore

    fishhore Member

    Joined:
    Aug 15, 2014
    Crap sorry it’s a ez 1.0 also
     
  4. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    The dual plane intake causes unequal cylinder fueling.

    The single plane will allow a smooth even idle at 700 rpm. F/A will improve for more power and better mileage. You will also be able to improve the engine timing for all of this to occur. You'll be surprised with all the improvement once you dial everything in for the single plane intake. This forum is filled with improvements noted after switching to a single plane intake with TBI fuel injection.

    Dual plane intakes are designed only to enhance carburetor venturi effect. Dual plane intakes upset TBI fuel metering and distribution. Using that dual plane, you just think your engine is tuned. It isn't right now by a longshot.
     
    Last edited: Apr 17, 2018
  5. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Your 4-speed will always be a problem as the adaptive learning can't be turned off in the EZ EFI 1.0. The single plane and new tune will lessen that issue for you. You may also need to go to a more stock heat range plug like the BKR6E with the single plane intake.
     
  6. A A

    A A Well-Known Member

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    Jun 22, 2014
  7. fishhore

    fishhore Member

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    Aug 15, 2014
  8. fishhore

    fishhore Member

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    Aug 15, 2014
    Idle is 750 btw. Can’t see that in the glare
     
  9. A A

    A A Well-Known Member

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    Jun 22, 2014
    Your .050 duration is mild. Larger cams tend to exacerbate the problems experienced with dual plane intakes. Be sure to check you have the latest ECU firmware for the retrofit screen 2.38/005.
     
  10. A A

    A A Well-Known Member

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    Jun 22, 2014
  11. fishhore

    fishhore Member

    Joined:
    Aug 15, 2014
  12. fishhore

    fishhore Member

    Joined:
    Aug 15, 2014
    This is doing about 50mph down the highway. How do all my numbers look to you? I will try unplugging my monitor from the ecu and see if that changes anything. I’ll also look to see what software I have. It is a odd sounding missfire to me. During moderate accel it is gone, during cruise it sounds very sporadic like and sometimes gargles during transitions in throttle. But the car cold starts just fine, warm starts great, it’s just got a small hiccup I can’t figure out
     
  13. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Everything looks good with the exception of the Inj DC % seems low. What ECU firmware do you have? How do the plugs look? What plug wires are you using? Also, what is your fuel pressure?
     
  14. A A

    A A Well-Known Member

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    Jun 22, 2014
    Another exception is your cruise A/F should be leaner than the idle A/F.
     
  15. fishhore

    fishhore Member

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    Aug 15, 2014
    I usually run cruise af @13.8 but had richend it up the day I took that data picture just to see if it cleaned up but it did not. And I’ll check everything else for you when I get home later.
     
  16. fishhore

    fishhore Member

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    Aug 15, 2014
  17. fishhore

    fishhore Member

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    Aug 15, 2014
    Fuel pressure is correct at power on not running. Msd 8.5 super conductor wires. Ngk BKR6E as recommended by their tech line.
     
  18. fishhore

    fishhore Member

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    Aug 15, 2014
    Oh also just went for a drive with the monitor unplugged from the computer and noticed no difference.
     
  19. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Well, right off, you have an EZ EFI ECU issue that has to be corrected. Contact FAST Tech for an RMA. You will need to send your ECU in to FAST for the correct update - 238/005. FAST will do the update under warranty if you are the original purchaser of the system. This may be the reason for your overly rich F/A ratio readings for what is a basically a mild street performance cam, and is in part the cause of what you have described. Your cruise A/F reading should be in the 14.7 range. This ECU firmware issue must be corrected first.

    You haven't mentioned how the plugs look, but I expect they don't look normal across all cylinders. With all your issues corrected, A/F ratios for your engine should improve considerably. WOT should also be 12.6-12.7.
     
  20. fishhore

    fishhore Member

    Joined:
    Aug 15, 2014
    AA, I’m going to call fast in the morning about the update. Why can’t they email it or have it for download? Also I want to order a single plane intake. Currently have the rpm air gap with a 1” spacer so I can fit a taller intake, so do u recommend the Vic jr, super victor or the rhs that fast sells. I have blue print brand aluminum heads.
     

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