Sometimes runs very rough then smooths out

Discussion in '7.3L Powerstroke Diesels' started by BigRedWeather, Jan 13, 2012.

  1. BigRedWeather

    BigRedWeather Full Access Member

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    WHEN IT HAPPENS: sometimes in cold weather, but many times in cold weather it does not happen. It just seems to happen when it wants to, not because of any set of confitions.

    WHAT HAPPENS: The truck will start and run kind of rough, like it is missing 2 cylinders, or very rough, like it is missing 5 cylinders. The amount of power it has corresponds to how many cyliners it seems to be running on. When it is very rough, I have to put it in 4 wheel Lo to back it out of my gently sloping driveway.

    WHEN IT STOPS: After I have driven for about 5 minutes at up to 2000 RMP it will run smooth as silk with all the power it normally has. It will do 90 on the interstate easily.

    My injectors have 150k to 200k miles on them. I can't understand why they would operate so poorly and then run so smoothly.

    It only runs rough for 5 minutes after I have started it.


    Any ideas?

    Thanks,


    BigRedWeather
     
  2. OLDBULL8

    OLDBULL8 Good Morning Ya'll.

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    Have you ever checked the UVCH harness under the valve covers? Loose connections there will cause that.
     
  3. BigRedWeather

    BigRedWeather Full Access Member

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    Let me think through this with you...

    If the injectors weren't getting the proper signal because of a faulty harness I could understand that the truck would run very rough, but I don't see why that would only happen for the first 5 minutes of driving and then disappear for the next 5 hours.

    If it is a faulty connection in the harness I could see the rough running 1 out of 3 times I start it and not the other 2 because the connection comes and goes.

    I have no conclusions yet, I'm still asking questions.

    More comments from you would be welcome, oldbull8.
     
  4. 94f450sd

    94f450sd Supporting Member Supporting Member

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    does it make a loud hissing sound when it does this?
     
  5. OLDBULL8

    OLDBULL8 Good Morning Ya'll.

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  6. 94f450sd

    94f450sd Supporting Member Supporting Member

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    Yes the 94-97 have 2 connectors on each head.but 95% of the complaints during the winter are caused by the ebpv.wich is normal.
     
  7. BigRedWeather

    BigRedWeather Full Access Member

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    Thanks OldBull8. I was checking my GPs last weekend and only got to those on the passenger side, so I have disconnected and connected those connectors. I will check the other side.

    94f450sd, No, it does not make a loud hissing sound. I am getting a handle on what happens with the EBPV system, but don't know it in detail. Does anyone know a good web page that details exactly what happens?

    The Sensor tells the regulator to change the flow of oil into the actualtor that moves the linkage to open or close the valve. I assume the valve closes when you start up on a cold day, but it must leave a hole for some exhaust to get out or the engine would stall.

    I'm going to go put my head under the hood and see what I find.

    Thanks for the input, past and future


    BigRedWeather
     
  8. BigRedWeather

    BigRedWeather Full Access Member

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    What do you suspect is happening, the valve is opening or closing at the wrong time? What do you suspect is causing that, the sensor, regulator, actuator?

    It helps me solve a problem to know the why, and not just the what. So if you suspect what is going on, I would appreciate the why behind it, if possible.

    Thanks,


    BigRedWeather
     
  9. powerhungry07

    powerhungry07 Registered User

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    Stupid question I was reading this thread I have some of the same Problems just always took it as it's not warmed up yet.when driving it in the cold I hear a hissing /vAcum sucking noise and I can watch my rpms slowly drop and the truck slow down. It's probably something simple but idl and with me being new at this and seeing it come up in conversation I figured I'd ask. thanks
    P.S. Sorry BigRedWeather for using your thread to ask
     
  10. BigRedWeather

    BigRedWeather Full Access Member

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    I don't hear the sound of sucking air. Our symptoms seem similar by not identical.

    My next step is to see if there are any codes and go from there.


    BigRedWeather
     
  11. 94f450sd

    94f450sd Supporting Member Supporting Member

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    Yours is the ebpv.completely normal.on the compressor side of the turbo there is a black plug bolted to the turbo.unplug it if this bothers you.its function is to close off the exhaust to force the motor to warm up on cold starts and during extended idling
     

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