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Thread: Smoke during idle

  1. #1
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    Smoke during idle

    I performed a cam swap and have some smoking at idle. I replaced the valve stem seals with dual valve springs. I am curious if I am seeing a burning oil issue or too much fuel issue. The smoke looks to be on the light blue side, which typically means oil. It takes about 10 minutes before I see smoke at idle. I just started working the tune, good start up and idle.
    During driving seems to go away, but when I accelerated the car back fires and sounds like it's running pig rich. The STFT at idle look good. I've attached the file and links to a couple of vids, one of smoking in cylinder number 1 and one showing the smoke externally. This all appears to be happening on bank 1.
    The heat readings on the left bank are cooler by average 75 degrees using a digital thermometer. I pulled bank one plugs and they are black with number being the worse. I swapped them and same scenario after driving a few miles.
    https://youtu.be/dVosXi-8W94
    https://youtu.be/f8SLr-7pTB8
    Attached Files Attached Files

  2. #2
    I would suggest cutting 5% of the fuel across the board and re-enable your LTFT. Not sure why you disabled those. Using both LTFT and STFT is a good way to dial in your idle and part throttle fueling.

    Roger

  3. #3
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    Quote Originally Posted by regorih View Post
    I would suggest cutting 5% of the fuel across the board and re-enable your LTFT. Not sure why you disabled those. Using both LTFT and STFT is a good way to dial in your idle and part throttle fueling.

    Roger
    Using STFT only will do the exact same thing as LTFT+STFT unless he's way out beyond what STFT only can correct.
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  4. #4
    21ms injection times on a DI engine are insane! Should generally be seeing a max of around 5.5ms, after which you're considered out of fuel.
    What is fuel pressure doing?
    Log fuel rail pressure. I feel like there is a problem there...
    With just a quick look, your airmass tables don't show any sudden jumps that would cause the injection time to jump so high.

    Also, add dynamic airflow to the list of things to log. Sometimes it helps to see airmass. I use it as a good check on everything.

  5. #5
    Senior Tuner mbray01's Avatar
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    did you install the spacer between the fuel pump when doing the cam.
    Michael Bray
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  6. #6
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    I installed the spacer, that is fine. Rail pressure is fluctuating around 58 psi.
    Number 1 cylinder is wetting the spark plug. I changed the already new seals for number one and the same thing.
    I am going to pull that head if I can't figure out what's the issue.
    I set timing like I normally would on c5 and c6.. Timing gear 6 oclock and sprocket 12 oclock. Just looked at Alldata and they have it as both at 12 oclock for TDC. If that is correct, then I screwed something up. Can anyone confirm it 12 and 6 or both 12?

  7. #7
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    Quote Originally Posted by [email protected] View Post
    I installed the spacer, that is fine. Rail pressure is fluctuating around 58 psi.
    Number 1 cylinder is wetting the spark plug. I changed the already new seals for number one and the same thing.
    I am going to pull that head if I can't figure out what's the issue.
    I set timing like I normally would on c5 and c6.. Timing gear 6 oclock and sprocket 12 oclock. Just looked at Alldata and they have it as both at 12 oclock for TDC. If that is correct, then I screwed something up. Can anyone confirm it 12 and 6 or both 12?
    that would be your low fuel side pressure, need to log fuel rail pressure as suggested by proxses

  8. #8
    Senior Tuner mbray01's Avatar
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    [/QUOTE]I set timing like I normally would on c5 and c6.. Timing gear 6 oclock and sprocket 12 oclock. Just looked at Alldata and they have it as both at 12 oclock for TDC. If that is correct, then I screwed something up. Can anyone confirm it 12 and 6 or both 12?[/QUOTE]

    cam gear at 6 or 12 is the same thing, cam turns once to every two crank revolutions.
    Michael Bray
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  9. #9
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    Rail pressure

    I logged the rail pressures.
    Review and let me know what you think.
    Attached Files Attached Files

  10. #10
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    8 degrees of knock with 10.9ms inj pw?! Wish I knew more to help but those are crazy figures. Most I ever seen was 5.9ms on e85 overly rich .790 lambda wot but now I am around 5.1 and .850s on my 19 ss a10. best of luck figuring it out

  11. #11
    Senior Tuner mbray01's Avatar
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    So back to my question, is the spacer actually on the follower, underneath the pump

    your desired fuel rail pressure should be over 800 psi per your posted tune(that needs to be properly re-calibrated) however your getting under 100psi, something is totally wrong mechanically
    Michael Bray
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  12. #12
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    Did you measure for you lash cap. Each cam needs to be measured for the right lash cap. I failed two HPFP becasue TSP kept saying I needed the comp cams lash cap for my L86. Then I found the thread below and measure and found out I needed the LS7 lash cap. My fuel trims where all over the place.

    My HPFP started chirping like a lifter went bad.


    https://www.corvetteforum.com/forums...learances.html

  13. #13
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    You either have a broken hpfp or the lifter isn't making contact looking at that log.

  14. #14
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    I just looked at you first log and looks how mine looked when my HPFP was failing. look at the STFT bank 1 and STFT bank 2 are always different at idol. Mine did the same thing before I figured out I had the wrong size lash cap. Now they pretty much read the same.

    What size fuel lob did you get. If it's 32% over like mine then I bet you have the wrong size on there. Our engines are almost identical and with the comp cams lash cap I was bottoming out by .018. The LS7 lash cap is .020 thinner than the comp cams lash cap. So now I'm I'm not bottoming out.

  15. #15
    Senior Tuner Higgs Boson's Avatar
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    I don't run a lash cap ever and have no problems. Every time I tried using a lash cap (in 2014) I had issues with it.

    Currently a BTR Stage II Blower Cam with 38% lobe in an LT4 with no lash cap, no problem.

  16. #16
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    Quote Originally Posted by Higgs Boson View Post
    I don't run a lash cap ever and have no problems. Every time I tried using a lash cap (in 2014) I had issues with it.

    Currently a BTR Stage II Blower Cam with 38% lobe in an LT4 with no lash cap, no problem.
    My cam and lt4 pump didn't even come close to requiring one either after measuring.

  17. #17
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    If you have a bigger fuel lobe and a LT4 HPFP it measure out that you don't need a lash cap. But with a 32% over and the stock LT1 or L86 HPFP you need a LS7 .060 lash cap. But I still would measure it first.

  18. #18
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Jonblarc7 View Post
    If you have a bigger fuel lobe and a LT4 HPFP it measure out that you don't need a lash cap. But with a 32% over and the stock LT1 or L86 HPFP you need a LS7 .060 lash cap. But I still would measure it first.
    The LT4 pump is a stroked LT1 pump.

  19. #19
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    Quote Originally Posted by Higgs Boson View Post
    The LT4 pump is a stroked LT1 pump.
    Correct but because of that longer stroke. Is why you don't need a lash cap with a LT4 pump.

  20. #20
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Jonblarc7 View Post
    Correct but because of that longer stroke. Is why you don't need a lash cap with a LT4 pump.
    correct, just pointing out that I don't recommend one with an LT4 pump, including on an LT1 with the pump swapped over.

    lots of people upgrade to LT4 pumps and cams.