97 12.7 idle issues

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by OhioHotshot, Dec 9, 2019.

  1. OhioHotshot

    OhioHotshot Light Load Member

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    Oct 21, 2012
    Cleveland,Ohio
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    Hello guys

    I'm having a issue with my ddec 4 I have repeated engine codes going on. Here's what's happening the truck idles rough up to about 1k rpm in park position runs fine going down the road. My mehanic at the terminal is saying it's a optimized idle issue from the the ecm, but the kicker my truck doesn't have that feature. So before I shell out for a new ecm, could this possible be a swapped ecm that's causing this issue?
    Thanks in advance for your help
     
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  3. jamespmack

    jamespmack Road Train Member

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    Start with frame to block ground wires. That is normally what I have seen.

    Simple, clean a spot on frame and block. Clamp on a jumper cable and set if it smooths out. Had one that loped like a 2 stroke and changed rpm with blower motor switch. Someone left the ground loose on the block.

    Or does it still have a APADs controller for A/C system? If so unplug it once and see what happens.
     
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  4. benjamin260_6

    benjamin260_6 Medium Load Member

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    Does it stop doing it when you release the parking brake?
     
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  5. OhioHotshot

    OhioHotshot Light Load Member

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    Oct 21, 2012
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    Where is that APADs located I'll check that later tonight.. Thanks for your input..
     
  6. OhioHotshot

    OhioHotshot Light Load Member

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    Cleveland,Ohio
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    No sir still does it. With brakes released
     
  7. jamespmack

    jamespmack Road Train Member

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    What year and model? I just recall some 2000/1999's Centurys having them above the right front steer wheel. When they crapped out, it logged all kinds of false codes and non existing codes in ECU.
     
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  8. OhioHotshot

    OhioHotshot Light Load Member

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    Oct 21, 2012
    Cleveland,Ohio
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    I stopped a tried the brake release and here's what happened. After releasing the brake the rough idle stopped then came back on a softer rough idle and its was sporadically versus continuous.. So whatever your thinking might help... Thanks
     
  9. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    Have "half engine mode" turned off in your ECM. You will need DDDL 6.45 on laptop to do that.
     
  10. benjamin260_6

    benjamin260_6 Medium Load Member

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    Ontario, Canada
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    As QUALITYTRUCK mentioned, I was thinking the half engine mode might be turned on. It can be set to come on without the parking brake but that's rare. If you turn it off, depending on which engine model it is, it might smoke a lot when it's cold
     
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  11. OhioHotshot

    OhioHotshot Light Load Member

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    Cleveland,Ohio
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    It's a 1998 century 12.7
     
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