She's getting better but....

Discussion in 'Freightliner Forum' started by dajain, Oct 30, 2022.

  1. dajain

    dajain Bobtail Member

    Apr 16, 2022
    1999 Freightliner FLD120, Cummins N14 with Eaton 10 speed for reference. Over a million miles.

    Still working the bugs out of the old girl. Finally used her this weekend for what I got her to do. She did really good but here are a few issues I would like to get fixed.

    1. The motor will occasionally go into a limp mode and it feels like power restriction and the rpm's are limited to 1500 rpm. Go a few miles and she picks right up again and starts pulling great again. No fault warnings or lights. Any ideas what system/sensor would cause a limp mode without a light?

    2. The idle control & jake brake quit working. Found the clutch pedal switch is loose and should be a simple fix when I get to it.

    3. After running for about 30-45 minutes, the tach does something weird. It doesn't quit working but it drops down approximately 1000 rpm. Be running 1500 rpm and the tach reads 500 rpm. Really no big deal as I am becoming more familiar with the truck sounds and feels at the right rpm's but still enough to want it to get fixed

    Biggie is the limp mode situation. Am I going to need to get the freightliner adapter for my Snap-on scanner to get a proper diagnosis? I would imagine.
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  3. lilillill

    lilillill Sarcasm... it's not just for breakfast

    Nov 7, 2007
    Possum Booger, Alabama
    Sounds like poor electrical connections. I'd just start under the hood, unplugging every connection one at a time. Then plug in, unplug, plug in, unplug... etc, then a shot of silicone spray and reconnect.
    dajain and RJM1953 Thank this.
  4. AModelCat

    AModelCat Road Train Member

    Jul 7, 2015
    Injector drivers in the ECM are known to deteriorate over time as well.
    dajain Thanks this.
  5. ducnut

    ducnut Road Train Member

    Dec 31, 2010
    While you’re under the hood, check both of the front brake air hoses for wear, right by the frame rails. It’s common for them to rub through on the back side of the hose, from contacting the frame.
    dajain Thanks this.
  6. Magoo1968

    Magoo1968 Road Train Member

    Mar 18, 2021
    St Malo mb
    Could be a corroded ecm fuse at battery . That wouldn’t throw a code most times . I’d start with easy stuff like clean grounds and positive connections another thing many people have found . By adding a extra ground cable to engine problems went away ..
    dajain Thanks this.
  7. lester

    lester Road Train Member

    Jan 2, 2012
    NW, Iowa
    Change fuel filters?
    dajain Thanks this.
  8. dajain

    dajain Bobtail Member

    Apr 16, 2022
    That's what I was thinking. Maybe just a simple connection issue. When I dig into it, I'll use the electrical connection cleaner, compressed air and then the silicone and hope I correct the issue without even finding it. lol

    I did see a little white in that fuse holder. I'll do it when I'm doing the rest of the connectors. Wouldn't hurt.
    I did run a new ground to the frame and ran a second ground straight to the starter. You can never have too many grounds IMHO.
    Magoo1968 Thanks this.
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