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torque converter clutch "hunting"

Discussion in 'GM Powertrain' started by cascott325, May 19, 2009.

  1. cascott325

    cascott325 New Member

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    i have a question which could be caused by a faulty something or another in the fuel/air monitoring system. my truck, usually when maintaining a speed between 43 and 53 mph, not at any certain rpm, will kinda rev up and down, up and down, up and down... etc, almost like its about to down shift but it doesnt, it just keeps pulsing like that until i mash the gas a little more, and it normally only happens when i am going up a slight-moderate incline. do any of you think it could be due to a faulty O2 sensor, or maybe dirty injectors? or if it is another problem, i will post it in its proper place, but if it is related to a bad sensor then whatever. i also noticed it this weekend when returning from tenn, it did it but not as bad, at around 85 or so
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  2. MrShorty

    MrShorty Moderator

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    Sounds to me more like a transmission issue -- specifically like the torque converter clutch (TCC) is engaging/disengaging because the computer can't decide for sure what it wants to do. Does it do it if you drop the selector into D?
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  3. cascott325

    cascott325 New Member

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    no, just in overdrive
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  4. MrShorty

    MrShorty Moderator

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    Really sounds like the TCC locking and unlocking. What happens is, in 4th gear, the computer decides the load is easy enough, so it locks the TCC. Locking the TCC increases the load on the engine just enough that the PCM decides to unlock the TCC. And so the PCM vacillates back and forth between locking/unlocking the TCC until you substantially increase the load (smash the throttle) or decrease the load (get over the top of the hill/downshift into 3rd). If this is your only symptom, I don't know how much I'd worry about it. Just get into the habit, when the transmission is "hunting" like that, simply downshift manually.
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  5. cascott325

    cascott325 New Member

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    thanks mr shorty. sorry for kinda changing subject.
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  6. noahraysanders

    noahraysanders New Member

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    how can you fix this

    how can you fix this?
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  7. MrShorty

    MrShorty Moderator

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    I assume you are looking for a solution other than manually downshifting into third gear.

    Assuming no mechanical problems are present, and you are sure it is just "hunting" the first thing that comes to my mind is a custom tune that changes the PCM's thresholds for locking/unlocking the TCC.

    PS extracted these posts from O2 sensor thread and put them in their own thread.
    Last edited: Jun 1, 2009
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  8. Jimmiee

    Jimmiee New Member

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    I believe he's fighting a surging problem and not a TC problem according to his other post he posted today.
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  9. cascott325

    cascott325 New Member

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    thank you moderator who moved these posts. i am sorry i started a new topic. i planned on trying to copy and paste to a new thread, but you beat me to it.

    back on topic... i have noticed that since my fuel pressure has been acting up, it seems to be more prominent of a problem, yet still only happening going up hills, i think the problem causing my offset psi's is causing the strange fluxuations in power as well... hmmm, who'd of thunk it
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  10. MrShorty

    MrShorty Moderator

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    How is your fuel pressure fluctuating? I can't think of a better term, but the fuel pressure is "moderated" by engine vacuum. When engine vacuum is high (indicating less load on the engine), fuel pressure will decrease a little. When engine vacuum drops (indicating more load on the engine), fuel pressure will increase. If your fuel pressure is fluctuating consistent with engine vacuum, it probably is related to the changes in engine vacuum caused by changing load on the engine caused by the TCC locking/unlocking.
    #10
  11. cascott325

    cascott325 New Member

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    i guess i worded it wrong, my pressure isnt fluctuating, its the power tha is doing it. its super hard for me to describe even in person. the only true way is to show you. i will try to catch a video of it one day soon and post it.

    i understand what you are saying about the converter, i just dont know how they work. i am sure they wear out eventually, but could this be a way of it showing me that it is on its way to failing, or is this normal for it to happen. i usually solve the problem by hitting the tow haul button or shifting down. im kinda gettin frusterated trying to explain what i am experiencing. i will get a video hopefully tomorrow
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  12. Jimmiee

    Jimmiee New Member

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    It doesn't sound like a Torque Converter problem to me. If your Torque Converter acts up it will set a trouble code immediately. Your problem sound more like a fuel or electrical problem. Have you checked for codes? Many codes will not turn on the Check Engine Light.
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  13. cascott325

    cascott325 New Member

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    yes. i use my diablo sport tuner to check about twice a month. no codes at all are thrown
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  14. noahraysanders

    noahraysanders New Member

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    i am having this same problem with my 2002 silverado 5.3 , i have tries everything i even took it to two mechanics and they couldnt figure it out..i hope someone comes up with a solution..
    #14
  15. Jimmiee

    Jimmiee New Member

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    This post morphed into 2 different problems. What exactly is the problem with your truck?
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  16. noahraysanders

    noahraysanders New Member

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    rpm surging between 40-50mph
    #16
  17. Jimmiee

    Jimmiee New Member

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    If you could find someone with a scanner that shows data you could pinpoint your problem in a hurry.
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  18. silveradotrailblazer

    silveradotrailblazer New Member

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    torque converter clutch hunting

    Have you tried installing your stock tune back in your truck to see if problems stops?
    #18
  19. cascott325

    cascott325 New Member

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    with or without the tune, it still happens. i was hoping that after a tune, it would pan out, but still does it. i am still trying to get a video. i know just the place, just havent had time to go there.

    i have been thinking about the scanner thing, i guess i should do that then. i will keep y'all posted.
    i did have my scanner plugged in today watching for misfires, at idle, i am showing slight misfires in all cylinders. not all at once, and not every one per cycle. they rarely count over 8 per cycle in 6, 7, and 8, and rarely over 6 counts in 1-5. but per cycle, it might show only 3 or 4 cylinders with misfire per cycle. once i start accelerating, and once i am at a constant speed or rpm, there is no longer a misfire in any cylinder.
    #19
  20. noahraysanders

    noahraysanders New Member

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    My rpms surge when im driving 40-50 mph.
    This is what ive done to try and fix it
    new mass air flow sensor
    new throttle sensor
    new fuel filter
    cleanened throttle body

    service codes are
    PO 137 02 signal low bank 1 sensor 2
    PO 172 fuel rich bank 1
    PO 175 Fuel system rich bank 2
    PO 332 Knock sensor 2 signal short/low

    ive replaced my o2 sensor before and it didnt correct the problem

    i have an 2002 5.3 silverado please help.
    #20

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