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  1. #1
    Legend cascott325's Avatar
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    Default torque converter clutch "hunting"

    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
    2000 silverado with a 5.3l v8, shorty headers, upgraded plugs, 10 mil wires, magnaflow high flow cats, flowmaster 80 series muffler(2 in 2 out) w/ 18 inch stainless silverline tips. i have a k&n CIA. its a 4x4 z71 offroad package. Ls model.
    extended cab 160k miles, truxedo low profile bed cover, diablo sport predator tuner.
    reman tranny @ 130k miles
    Chris

  2. #2

    Default

    Quote Originally Posted by cascott325 View Post
    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
    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?
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
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  3. #3
    Legend cascott325's Avatar
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    Default

    Quote Originally Posted by MrShorty View Post
    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?
    no, just in overdrive

  4. #4

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    Quote Originally Posted by cascott325 View Post
    no, just in overdrive
    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.

  5. #5
    Legend cascott325's Avatar
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    Default

    thanks mr shorty. sorry for kinda changing subject.

  6. #6

    Default how can you fix this

    Quote Originally Posted by MrShorty View Post
    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.
    how can you fix this?

  7. #7

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    Quote Originally Posted by noahraysanders View Post
    how can you fix this?
    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 by MrShorty; 06-01-2009 at 05:25 PM. Reason: moderation information

  8. #8

    Cool torque converter clutch hunting

    Have you tried installing your stock tune back in your truck to see if problems stops?

  9. #9
    Legend cascott325's Avatar
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    Quote Originally Posted by silveradotrailblazer View Post
    Have you tried installing your stock tune back in your truck to see if problems stops?

    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.

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