Cat Dead Spot

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by awright, Feb 21, 2023.

  1. awright

    awright Light Load Member

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    I have a cat C-15 MXS factory 625hp that has a complete PdI on it. In a 2006 Peterbilt 379. I get a dead spot in the throttle as i shift gears when taking off first thing in the mourning. Almost seems like my drive wheel slipped on a patch of ice, but only for a split second. I don't notice when loaded, or when truck has been running all day. I have replaced the tps on the foot pedal. Anyone have any ideas?
     
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  3. Smellfunny

    Smellfunny Road Train Member

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    What does the RPMS do when it does this?
     
  4. awright

    awright Light Load Member

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    I think they drop. It happens so quick, I will have to pay better attention to RPMS.
     
  5. bjytech

    bjytech Light Load Member

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    You could have one of the engine speed sensors dropping out (crank or cam), it will run fine just reading the one engine speed sensor, you probably have a code stored in the ECM telling which sensor but it will not throw the check engine light on for that code.
     
  6. awright

    awright Light Load Member

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    ok, thank you, I will have to check into those sensors.
     
  7. awright

    awright Light Load Member

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    Could either of those engine speed sensors have anything to do with my speedometer bouncing and a growl/shake when i go into a good pull at low rpms?
     
  8. bjytech

    bjytech Light Load Member

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    No, those sensors wouldn't have anything to do with that.
    Those issues you mention are common if the output yolk on the trans is loose which could be a sign the output shaft bearing is on its way out.
     
  9. awright

    awright Light Load Member

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    Ok. I have had yoke changed and output shaft checked multiple times. Driveshafts rebuilt and balanced. I just wonder if my " Reman" transmission was done with substandard parts. Next time it will be a new one. It was really growley today, so im guessing it wont be long. Thanks for all your help.
     
  10. awright

    awright Light Load Member

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    I do sometimes wonder if my ride height is off. I go to one shop, and they say it was 1.5" too high. I go a few months later to the next shop, and they say its .75" too low. There seems to be some disconnect in this area. I have the suspension that does not have the big horse shoe shaped springs, mine are just the standard springs and air bags. 2006 Peterbilt 379. What should my ride height really be at?
     
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