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Thread: help with my 4.8 with cam and long tube headers.

  1. #1
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    help with my 4.8 with cam and long tube headers.

    I'm brand new to tuning and have 0 knowledge of anything to be honest. Over the last year I took a shot at attempting my first build and decided to take my 2002 silverado 1500 and do a bit of work to it which includes:

    1 7/8" to 3" Long tube headers
    Valve Springs
    Summit 8706 Cam (275int /280exh)
    340lph Fuel Pump
    and a bit of supporting stuff (bigger aluminum radiator, electric fans, new fuel lines, brakes, brake lines, remanufactured 4l60e etc etc)

    It fires up and sounds pretty great at idle but anytime I go to give it gas it dies out right after, so I copied a tune I found on youtube and now it dies occasionally when I go from starting it to putting it into reverse or drive, or if I give it any gas in gear, but if it's in Park I can rev it to red line and it's fine... I'm not really sure what to do I just want to get it running decently to be able to take it to work and such until I can find a good tuner near me (Bergen County, NJ) to set up some dyno time and get things dialed in.

    I've included the current tune file in it. As well as a log for trying to get it up and down the driveway but like I said, it kept dying on me. I posted a little while ago but had a pretty bad vacuum leak but have fixed it since. I was hoping that would solve the issue but it still hasn't.. Any and all help is greatly appreciated.4.8 cam springs headers fuel pump.hplThe Mule Cam Springs Long Tube Headers lets hope this shit works.hpt

  2. #2
    Tuning Addict 5FDP's Avatar
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    Looks like it has flex fuel injectors too?

    The over/underspeed spark correction have the same value, that isn't right. One will be positive and the other negative. Look back at your stock file to see where you missed that and change the one to a negative value. Aim for +/- 8 to 10 degrees.

    Your idle speed is so high that it's idling with really high timing too. Drop the idle speed down to 850-900rpm and get the timing around 20ish degrees.

    Make sure the exhaust is complete too, that will throw the fuel trims for a loop if this still has open headers. A long log file would be helpful to see how the fueling is doing. A wideband is also going to be wanted because we can only do so much with the fuel trims. Also double check fuel pressure, should be around 52-58psi.

    If fueling is way lean because the fuel trims are showing very positive numbers you'll want to add fuel to the MAF and VE tables to bring the trims down.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Okay, so I lowered the idle rpm's as well as copied the stock over/underspeed spark correction, and I attempted to give it 20ish degrees of timing in Spark > Advance > Base > High octane... but i'm not sure if I did it right. I wrote the updated tune to the truck and it idles way healthier but as soon as I put it in drive it dies out and when I turned it back on it was surging... what am I doing wrong?4.8 cam springs headers fuel pump lower idle.hplThe Mule Cam Springs Long Tube Headers 850 rpm idle 20ish degrees timing.hpt

  4. #4
    Tuning Addict 5FDP's Avatar
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    Return the base running airflow back to stock and start over. To me you have added way too much there. Add like 20-30% and see what that does.

    The fueling is still lean as well. Add like 3-5% to the MAF and VE table.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  5. #5
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    Okay so I put stock running air flow and increased it by 20% as well as bumping MAF and VE tables up 3% and it got worse i think. It just immediately dies out when I put it in gear now.4.8 cam springs headers fuel pump lower idle v2.hplThe Mule Cam Springs Long Tube Headers 850 rpm idle 20ish degrees timing.hpt

  6. #6
    Tuning Addict 5FDP's Avatar
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    It's even more lean than the previous log and you lowered your idle speed more than I think you should have. I said try aiming for 800-900rpm

    Is your fuel pressure okay?

    Is the exhaust complete??

    You never answered on whether this is really running flex fuel injectors or not.

    This is not really an extreme setup, it should be able to run "okay" so long as it's got fuel and the timing isn't all over the place. Possible that stall saver is something to look at too, it could be making it worse.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  7. #7
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    It's not running flex fuel injectors, just the stock ones that came with it I'm not entirely sure how to check fuel pressure as I don't have a regulator/gauge. My exhaust is catless and has yet to be completed after the Y pipe merge. As far as the idle speed, at what temp should it start being around 800-900? Lastly what do you mean by stall saver? How would I get to that/remedy it? Thank you by the way for the input/help

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    Tuning Addict 5FDP's Avatar
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    This is where it gets frustrating, people should stop copying tunes from other people when they have no idea if it even matches stuff done to their vehicle.

    Whatever tune you copied from has 33lb/hr flex fuel injector data. If you have bone stock 4.8 from a 2002 truck, it will not have 33lb/hr injector. It will have 25lb/hr injectors. Now the tune needs to have the factory 25lb/hr injector put back into the calibration so fueling is far more correct.

    I would bet that this truck would run far better if you used your stock tune and just changed what you need to to make it run. Like the idle rpm settings, higher base running airflow, timing settings.

    Make it idle at 800-900rpm basically everywhere while you figure things out. Then you can slowly lower the idle rpm down to 700ish once fueling is correct and timing is all figured out.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  9. #9
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    so I followed your advice and it drives on it's own power finally but i noticed when i'm slowing down to a full stop it almost dies out, the rpm's drop like crazy.. I'm attaching a log, any chance you could let me know what paramaters I need to change to get it working better? Thank you again for all your help so far.first drive.hpl

  10. #10
    Advanced Tuner TheMechanic's Avatar
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    Did you reset your fuel trims after the write?

  11. #11
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    I did not, I?ve got to do it through the scanner if I?m not mistaken.. what does resetting the fuel trims do?

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    Advanced Tuner TheMechanic's Avatar
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    Fuel trims a way the computer can modify the amount of fuel that is injected to compensate for changes/differences in an engine. The "Tune" will have no running compensation. After the engine has run and compensated in a positive/add fuel or negative/remove fuel it stores it in a non volatile memory. When you change something you need to bring it back to no correction to see if you have the tune right. The idea is to get it to a point where no matter what you ask of the engine it is always at or near zero correction. These corrections can be somewhat slow. That is why resetting them is generally a first step before starting it up and doing a test drive or recording.

  13. #13
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    oh nice, that makes sense. So double checking in order to reset the fuel trims i would connect to the vehicle through the scanner, go to controls & special functions, then click Reset LTFT. At that point can I just disconnect from the vehicle and it's all done?

  14. #14
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    Quote Originally Posted by TheMechanic View Post
    Fuel trims a way the computer can modify the amount of fuel that is injected to compensate for changes/differences in an engine. The "Tune" will have no running compensation. After the engine has run and compensated in a positive/add fuel or negative/remove fuel it stores it in a non volatile memory. When you change something you need to bring it back to no correction to see if you have the tune right. The idea is to get it to a point where no matter what you ask of the engine it is always at or near zero correction. These corrections can be somewhat slow. That is why resetting them is generally a first step before starting it up and doing a test drive or recording.
    So I reset the LTFT and went on a decent drive logging today, seemed much better but still dies out when I go into reverse, any idea what it could be?3rd drive.hplMostly Stock Tune slight adjustments.hpt