X15 Cummins knocks under acceleration

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Brandon0928, Dec 3, 2022.

  1. Brandon0928

    Brandon0928 Light Load Member

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    2017 x15 knocks under acceleration .Loaded or empty. Gets noticeably worse when you get to 1500 rpm and around 63mph. At idle you can run it up to 1500 and doesn’t knock.
    2018 579 Peterbilt. Sounds like it’s coming from the valve train but hard to judge going down the road . What could it be ? Took it to 2 different places and they couldn’t find anything. Have noticed a slight turbo surge at idle last week. And the air intake makes a “popping” noise while compressor is running
     
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  3. Brandon0928

    Brandon0928 Light Load Member

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    Did injector rail test and that passed . Did cutout test. Passed . Truck still runs good with no power loss. Sometimes it feels like the knock can also produce a “shake”
     
  4. Brandon0928

    Brandon0928 Light Load Member

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    I can be going 65 in 13th gear at 1300rpm with boost at 30 and barely hear it . Drop back to 12th going going 65 at 1550 rpm it knocks. The second you let off throttle it goes away
     
  5. Tropsnart

    Tropsnart Road Train Member

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    I'd start with new fuel and air filters if it's not doing it unless it's under load. I had the same popping noise on my 2018 x15 from the air compressor. It sounded like garbage but never amounted to anything. I just made sure all the connections were tight and sampled the oil regularly.
     
  6. Brandon0928

    Brandon0928 Light Load Member

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    did oil sample last week and came back good . New air filter . New fuel filter. Oil change
     
  7. runningman0661

    runningman0661 Road Train Member

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    I have a 2018 X15 every year I have the shop run an overhead, two years ago they noticed cam lobe wear, but it was “within spec” 6 months ago during my annual overhead it had gotten progressively worse. So I replaced the cam and all the rockers. Cummins has had cam issues, not sure if this would cause the issue your having, but you should look into it.
     
  8. Short Fuse EOD

    Short Fuse EOD Road Train Member

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    Have the same thing on a 22. Remounting the fuel pump, timing was off helped a little. Still have the issue. Same as you describe. 1500-1600 rpm heavy pull mostly in 17 gear. Cummins and Pete say don’t worry bout it. Gonna run till she blows and put in a 60 series more than likely.
     
  9. Brandon0928

    Brandon0928 Light Load Member

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    So stack is covered in white. Missing a quart of antifreeze. Also noticed that the truck has the same shake while using engine brake. This is a bummer
     
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