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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
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  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
    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

  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.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  5. #5
    Legend cascott325's Avatar
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    Default

    thanks mr shorty. sorry for kinda changing subject.
    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

  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

    Default

    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
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  8. #8

    Default

    Quote Originally Posted by MrShorty View Post
    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.
    I believe he's fighting a surging problem and not a TC problem according to his other post he posted today.
    Jim

    2004 SILVERADO 2500HD LS
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  9. #9
    Legend cascott325's Avatar
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    Default

    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
    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

  10. #10

    Default

    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
    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.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

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