Transmission acting funny
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HT4100 4.1, 4.5, 4.9 Discussion, Transmission acting funny in Cadillac Engine Technical Discussion; ...
  1. #1
    83CADMAN's Avatar
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    Question Transmission acting funny

    I took care of the small gasket leaks I found when replacing the water pump on my 83 Eldo’s HT4100. I cleaned, waxed and gassed it up for some summer driving. The car was running sweet.
    One day I went on a drive through the rolling hills to the south of where I live. Because of the hills the car kept downshifting, just as it should. But then the car started to act like the engine was missing on 3 cylinders. Sort of like a slight lunging in the drive train. I managed to get home and parked it in the garage. The next morning I started it up and PURRRR just like a kitten. Huh I thought to myself as I shifted into gear only to feel the same slight lunging. Reverse, Drive, didn’t matter. Neutral, runs smooth.
    Now my Eldo is the 83 and has the 4 speed w/ torque loc converter.
    Has any one had any experience with this kind of problem? Any ideas are welcome before I go and lay down any cash on trany work.

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    ehall's Avatar
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    Re: Transmission acting funny

    I wouldn't jump straight to tranny, it might be something simple like TPS

  4. #3
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    Re: Transmission acting funny

    Quote Originally Posted by 83CADMAN View Post
    I took care of the small gasket leaks I found when replacing the water pump on my 83 Eldo’s HT4100. I cleaned, waxed and gassed it up for some summer driving. The car was running sweet.
    One day I went on a drive through the rolling hills to the south of where I live. Because of the hills the car kept downshifting, just as it should. But then the car started to act like the engine was missing on 3 cylinders. Sort of like a slight lunging in the drive train. I managed to get home and parked it in the garage. The next morning I started it up and PURRRR just like a kitten. Huh I thought to myself as I shifted into gear only to feel the same slight lunging. Reverse, Drive, didn’t matter. Neutral, runs smooth.
    Now my Eldo is the 83 and has the 4 speed w/ torque loc converter.
    Has any one had any experience with this kind of problem? Any ideas are welcome before I go and lay down any cash on trany work.
    Any trouble codes? How's the fluid? Look, smell, level?

  5. #4
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    Re: Transmission acting funny

    Tps?

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    Re: Transmission acting funny

    No codes, level good, fluid and filter changed about 200 mi ago, also flushed system. I had them do the cooling system as well.

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    Re: Transmission acting funny

    The computer controls the throttle when the car is at idle. It looks at a variety of inputs to determine how much gas to give (for example, one of the inputs is RPM). Basically the computer tries to keep the car from conking out when you load up the engine by turning the wheels (power steering pump) at a red light at the same moment that the A/C kicks on (compressor) which will increase load on the engine and kill it if it doesn't get more gas. If a sensor is off then it's possible for the computer to get the wrong input data. Or, if the idle speed controller is damaged, the computer won't be able to control the idle with precision (sticky or stuck and it won't respond like it should).

    If you only feel the engine jerk around when the car is in gear and stopped (but not when moving) then it's probably engine management. If you feel it all the time, you can start worry about transmission

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    Re: Transmission acting funny

    should'nt that kick a code?

  9. #8
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    Re: Transmission acting funny

    Which of the codes from 1983 do you think it should throw

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    Re: Transmission acting funny

    Just asking. If the problem lies with a sensor, which one might it be? I’ll check the ISC. Also what is TPS?

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    Re: Transmission acting funny

    Quote Originally Posted by 83CADMAN View Post
    No codes, level good, fluid and filter changed about 200 mi ago, also flushed system. I had them do the cooling system as well.
    Flushed with a machine? A lot of transmissions die after a flush. A perfect way to introduce someone else's transmission debris into your transmission.

  12. #11
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    Re: Transmission acting funny

    Quote Originally Posted by HUF View Post
    Flushed with a machine? A lot of transmissions die after a flush. A perfect way to introduce someone else's transmission debris into your transmission.
    I've enjoyed almost three years and a couple of hundred miles of trouble free motoring since flushing. I presume the shop used some type of machine to do the job.

  13. #12
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    Re: Transmission acting funny

    TPS is throttle position sensor, it's the thing that tells the computer the angle of the throttle blades, which is used to enable or disable other things. For example the TPS signal tells the computer when it should take control of idle speed, or when to engage the EGR solenoid (off at idle, on with throttle), and so forth. Later vehicles used this as input for the shift tables too, but on our generation the transmission is all mechanical. The point is that it is used for lots of things and if it goes bad it can trigger a lot of strange problems. I DO NOT THINK THE TPS IS YOUR PROBLEM just saying that you might have a simple problem and you should not jump to conclusion that your tranny is bad. Your tranny won't make the engine miss or surge.

    Can you describe the engine problem more fully

  14. #13
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    Re: Transmission acting funny

    Quote Originally Posted by ehall View Post
    Which of the codes from 1983 do you think it should throw
    I found in one of my ref manuals regarding the TBS (Throttle Position Sensor)..."A problem in any of the TPS circuts will set a trouble code 21 or 22." Recomends adjustment or replacement.

  15. #14
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    Re: Transmission acting funny

    Quote Originally Posted by ehall View Post
    The computer controls the throttle when the car is at idle. It looks at a variety of inputs to determine how much gas to give (for example, one of the inputs is RPM). Basically the computer tries to keep the car from conking out when you load up the engine by turning the wheels (power steering pump) at a red light at the same moment that the A/C kicks on (compressor) which will increase load on the engine and kill it if it doesn't get more gas. If a sensor is off then it's possible for the computer to get the wrong input data. Or, if the idle speed controller is damaged, the computer won't be able to control the idle with precision (sticky or stuck and it won't respond like it should).

    If you only feel the engine jerk around when the car is in gear and stopped (but not when moving) then it's probably engine management. If you feel it all the time, you can start worry about transmission
    O.K. I've looked in the books and find no ref to a "Idle Speed Controller". Is it a solonoid or something? Where is it located?

  16. #15
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    Re: Transmission acting funny

    Well I’ve run the on board diagnosis again and kicked a code “60” (Transmission not in DRIVE-cruse control circuit). My book says to clear the code, drive the car some and then recheck. If the code reappears take the car to a shop for further diagnosis. Well I guess I'll put the air cleaner back on and give it a shot.

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