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Thread: Help Please, Odd Chattering Noise

  1. #1
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    Help Please, Odd Chattering Noise

    Hi, I was wondering if anyone could help me out. I have a 2000 GMC Sierra 1500 with a 2008 LQ9 swapped in. The motor was completely rebuilt before install, everything torqued to spec. It runs great and pulls strong throughout the rpm range. I'm getting an odd chattering noise that I can't figure out and I'm wondering if its possibly tune related. Its only under moderate throttle and its not constant. Its kind of random

    I am currently running a stock 6.0 tune, as I am new to tuning and haven't quite jumped into tuning the truck myself. I have attached the tune and a log file if anyone could take a look for me it would be greatly appreciated.
    Attached Files Attached Files

  2. #2
    Tuning Addict 5FDP's Avatar
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    It's lean and you are picking up a lot of knock.

    The long term fuel trims are just about stuck at +25% showing that you have something wrong or it's untuned if the engine is not stock.

    You really need to verify fuel pressure and make sure it's within spec all the time. If that is good, start looking for vacuum leaks and exhaust leak pre-o2 sensor. Something is causing the fuel trims to show a lean condition. If it those low fuel pressure/vacuum/exhaust leaks or the engine is not just a stock 6.0.

    With that amount of knock you are showing, it could be possible that you are hearing the ping/chatter from that. I for sure would not be running 87 octane in a engine like that either. 89 octane or 91+ at a minimum. 87 octane is way too prone to knock.


    Start there and report back. Also you really need to log the o2 sensors themselves, your cylinder airmass and injector pulse width avg. Those are good things to watch and can tell you information on how it's running.
    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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    Quote Originally Posted by 5FDP View Post
    It's lean and you are picking up a lot of knock.

    The long term fuel trims are just about stuck at +25% showing that you have something wrong or it's untuned if the engine is not stock.

    You really need to verify fuel pressure and make sure it's within spec all the time. If that is good, start looking for vacuum leaks and exhaust leak pre-o2 sensor. Something is causing the fuel trims to show a lean condition. If it those low fuel pressure/vacuum/exhaust leaks or the engine is not just a stock 6.0.

    With that amount of knock you are showing, it could be possible that you are hearing the ping/chatter from that. I for sure would not be running 87 octane in a engine like that either. 89 octane or 91+ at a minimum. 87 octane is way too prone to knock.


    Start there and report back. Also you really need to log the o2 sensors themselves, your cylinder airmass and injector pulse width avg. Those are good things to watch and can tell you information on how it's running.
    Thanks! I'll check that in the morning. The only thing that's not stock about the motor is that the heads are shaved .040.

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    Okay so I checked fuel pressure and its around 58-60 psi with the truck off and key on. I don't have a way to check it with the truck driving. No vacuum leaks, and no exhaust leaks. Long term fuel trims still staying maxed out for the majority of the time the truck is running.

    I was also previously running 87 octane fuel, I had about a 1/4 tank of 87 left so I poured a little octane booster in the tank and filled up with 93. The majority of the noise is gone, however I can still hear it every now and then on moderate to hard throttle

    The motor is stock other than the heads being shaved .040

    6.0 stock tune log 2.hpl
    Channel config 1.Channels.xml
    Last edited by jwillie128; 08-23-2019 at 02:23 PM.

  5. #5
    Tuning Addict 5FDP's Avatar
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    Try to figure out a way to check the pressure while driving. Get a longer hose so you can tape it to the windshield and go for a drive.
    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.

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    Check the intake gasket, it sure looks like you have a vacuum leak.

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    Quote Originally Posted by 5FDP View Post
    Try to figure out a way to check the pressure while driving. Get a longer hose so you can tape it to the windshield and go for a drive.
    Fuel pressure was consistent between 50 and 55 psi while driving.

    Quote Originally Posted by DougO View Post
    Check the intake gasket, it sure looks like you have a vacuum leak.
    Intake gasket is brand new, I just rebuilt the top end about 2000 miles ago. I did check it though by misting water around the intake gasket and it didnt affect the engine at all.

    I did find a crack in the vacuum line between the throttle body and the passenger side valve cover and replaced it.

    I ran another log and LTFT weren't maxed out this time. I also only heard the chattering noise once while driving