6nz slight miss

Discussion in 'Trucks [ Eighteen Wheelers ]' started by KittyKicker, Dec 27, 2015.

  1. KittyKicker

    KittyKicker Light Load Member

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    I just did a platinum rebuild on my 6nz. Installed a marine cam and 7" straights. Other than that, the truck is stock. Everything seems to run fine at idle. Under load, it seems to have a slight miss that sometimes goes away. It doesn't smoke, no dummy lights. Also, with the new pipes I feel like I can hear one cylinder popping off over the others, almost like the jake brake at low speed but I'm standing on the throttle. I'm at the point that I can't tell if I'm engineering problems in my head or if there really is an issue. The motor was so worn out when I bought the truck that it ran like crap anyway, so I don't have a real before and after to compare it to. Help!
     
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  3. mountaingote

    mountaingote Road Train Member

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    Maybe a valve adjustment issue?
     
  4. KittyKicker

    KittyKicker Light Load Member

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    Well, I've had the overheads run twice. From all the research I could find, the valves should have been set to the same spec, regardless of the cam. Unless I'm wrong on that. But then why would it go away?
     
    mountaingote Thanks this.
  5. mountaingote

    mountaingote Road Train Member

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    I'm not a mechanic, but I'm trying to think of possibilities. Maybe one of the injectors has an issue, I know they're new but that doesn't mean trouble-free. I lost an injector once and the mechanic started looking at the rest and found 3 with broken springs. I'm not aware of anything else that might cause one cylinder to work differently
     
  6. Oxbow

    Oxbow Road Train Member

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    I am way out of my league here, but I have read that fls/fts codes for the injectors may need to be set. Hopefully someone with some knowledge on the injector trim codes will comment.
     
  7. KittyKicker

    KittyKicker Light Load Member

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    You mean that they have to be set any time an injector is replaced the codes have to be set?
     
  8. Oxbow

    Oxbow Road Train Member

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    I am not sure as I have only mechanical engines, but I have read that there is a number on each injector, and they can be set individually. If you have just had a platinum o/h though your shop should know about this and have done whatever is necessary. Where you have changed cams it may be that they should be set accordingly, I just don't know much about it. Hopefully someone who does will jump in here and let you know if I am all wrong or whatever.

    Sorry I can't be more help.
     
  9. KittyKicker

    KittyKicker Light Load Member

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    I appreciate any help I can get buddy. I wish I knew a lot more than I do, too.
     
  10. KAK

    KAK Medium Load Member

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    IF you didn't put on a new engine wiring harness at O/H I sure would. They are relatively inexpensive for a 6nz
     
  11. KittyKicker

    KittyKicker Light Load Member

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    Which harness are you referring to? I bought a new fuel injector harness but I haven't put it on yet. Is there another one I should worry about?
     
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