7.3 light throttle = hesitation

Discussion in '99+ 7.3L PowerStroke Engine & Drivetrain' started by grmjepr, Mar 9, 2010.

  1. grmjepr

    grmjepr SDD Junior Member

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    :rant, Ok here it is, I have tried researching as many hesitation threads as possible, and still are stumped. This is what I have. 2000 7.3 excursion. Last year my injector harness went so it was replaced along with the recall cam sensor. Shortly after I began noticeing a once in a while slight ruff idle. A few once down the road i had a hesitation/jerk with light throttle, and also while on cruise control. So off to the dealership it went. replaced # 1,3,and 8 injector, still no resolution. Cleaned back pressure sensor, nothin. Finally after going back to dealership they replaced my ICP. Truck then ran fine but still had ruff idle once in a while. Now about one year later, light throttle only, hesitation is back, worse than ever. I went back thru and replaced the ICP,cam shaft sensor, recleaned back pressure tube, and still nothing. WOT is perfectly fine. Now, if i start the truck "COLD" and immediately drive it, it is fine for about 5 minutes then the gremlins come out. I read a thread about the IDM possibly causeing my grief. I do run a SCT tuner on extreme, but do not beat my truck, I have also tried on stock tune. With extreme, problems are of course much more noticeable. extremely frustrated and ready to go back to spark plugs:eek:
     
  2. BIG JOE

    BIG JOE Full Access Member

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    Good steady Fuel pressure ?

    OBTW..... WELCOME to SDD ;tu
     
    Last edited: Mar 9, 2010
  3. grmjepr

    grmjepr SDD Junior Member

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    Dunno on the fuel pressure, but one thing i did forget to post is that when the gremlins come out, the " diesel motor typical knock sound " goes away for a brief moment, almost like one side not fireing, if you know what I mean, but under full throttle she is perfect.
     
  4. JLDickmon

    JLDickmon ursus combibo

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    how bad is the hesitation? is it a stumble, or is there a long pause of you pushing the go pedal to get it to go?

    any difference if you ease into the throttle or nail on it?

    can you feather the throttle and make it stay "hesitating?"
     
  5. grmjepr

    grmjepr SDD Junior Member

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    It is a short stumble. I played with it on the way home this morning " east coast, 47 degrees".

    very, very light pedal it will not do it.
    from a stop, normal pedal, it will stumble.
    off and on pedal, aggressively, no stumble.
    cruise control, stumble, when throttle comes on and off.
    normal driving, stumbles when letting off pedal, and back on.
    drive it like i stole, sorta goes away, then comes back.
    WOT, perfect, but cant stay under speed limit...lol

    changeing my oil and fuel filter in a few minutes...

    will check back in....thanks for the input!!
     
  6. BIG JOE

    BIG JOE Full Access Member

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    Do you have gauges ??

    Whats the boost pressure like ?

    Loose, cracked I/C boot(s) ? Air filter clean ? Stock Air filter ?

    Fill out the "Signature" feature in the User CP section.... If we know what you've done to your "X" it sure helps Us.. Help You.

    Joe
     
    Last edited: Mar 9, 2010
  7. grmjepr

    grmjepr SDD Junior Member

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    No gauges here, all stock X with SCT tune and K&n cone filter. Changed oil and fuel filter with no luck of killin the gremlin. I did get it to constant hesitation at 1600 rpm's and about 10% throttle, must be the sweet spot because again it will do it at any rpm but still about 10% throttle. Checked all tubes and made sure they were solid and tight. Read my codes : p0603 internal ctrl mod kam er.

    checked out the cp section and did not see a signature section.

    thanks again for the brain stormin!!
     
  8. BIG JOE

    BIG JOE Full Access Member

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    In the CP section yul see: Edit Signature.. thats where you can tell about yer X.

    Couple things:

    1. If your tuner has the capability to erase codes.. erase them. If not.. you can disconnect the Batts (both) for about 20 minutes.. that might erase the p0603 code. Do a test drive.. see what you get.

    2. At about 1600 rpm is where the 99.5 to 03 7.3 turbo has a "Surge" issue. Remove the whole intake.. all the way to the turbo inlet. With good light.. inspect the leading edges of the compressor wheel.. look for dings, pits or any chipped edges. They ALL should be Clean, Sharp, Strait and Uniform in color (grey-ish).

    Let us know what you find ??

    Joe
     
  9. dpantazis

    dpantazis #12

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    cackle? happens about the same RPM range.

    what is your fuel tank level. top it off to reduce/eliminate cackle.
     
  10. Tail_Gunner

    Tail_Gunner CRJ & ERJ A&P Mech.

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    Sevral years ago I was expereincing an occaaisional stumbling issue when going down the road. Sometimes, if idling the engine would buck & stall. I noticed the issue was more common after refueling. After I would experience a stumbling episode, I would drain the fuel bowl using the yellow lever and the bucking/ stumbling would cease for a while.

    I also noted these issues were more common during the late fall & early spring when the weather was very changable. (i.e. temp changes causing condensation in fuel tanks)

    I surmised that it may have been a fuel/water issue. So I installed a fuel filter water separator ahead of the fuel filter.
    [​IMG]

    Since I installed that filter, the truck hasn't bucked or stalled since.
    Was water in the fuel my problem?? I dunno for sure, but the timing of everything makes you wonder.
     
    Last edited: Mar 9, 2010

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