Surging Sonata

Discussion in 'Hyundai Sonata' started by mdqcumber, Oct 10, 2007.

  1. mdqcumber

    mdqcumber Guest

    The car runs smooth when idling, runs smooth when accelerating, but as the
    car gets close to the desired speed, it starts dropping rpms, then surging
    back up again. It's really hard to drive because the car is continously
    jerking.

    With the cruise set at about 73mph, it was running at about 2900rpms then
    it was hesitate the rpms would drop to about 2500rpms, it would surge back
    up to about 3100 rpms and then level out to about 2900 rpms. The intervals
    between it doing this would depend on the road (going up/down hills or
    flat surface)I would guess at least every 45 - 90 seconds. (Note: It does
    NOT matter what the speed I'm driving at, it continously does this. Also,
    the car will not shift gears until it reaches about 4000rpms regardless of
    the speed of the vehicle)

    I recently replaced the throttle position sensor (28 August 07) and the
    throttle body (22 September 07. After I replaced the throttle position
    sensor, it stopped surging for 1 day, after I replaced the throttle body,
    the car ran great for about three weeks, then it started surging again.

    Could anyone offer any assistance or advise to resolve this problem? I
    would really appreicate it.

    Tks, Mark
     
    mdqcumber, Oct 10, 2007
    #1
  2. mdqcumber

    Rob Guest

    It would help if we knew a little more about your Sonata, What year? What
    motor? What kind of transmission?

    Rob
     
    Rob, Oct 11, 2007
    #2
  3. mdqcumber

    Mike Marlow Guest

    Have you scanned this car yet? Sounds like the lock up is acting up, but
    I'm wondering what's going on with the high shift points.
     
    Mike Marlow, Oct 11, 2007
    #3
  4. mdqcumber

    Tom Guest

    Like Mike said, it sounds like the lock up converter is going in and out.
    It used to be that cars had a vacuum actuator for that function and
    sometimes the line would leak.
    How many miles are on it and what year? It could also be a plugged
    catalytic converter which would cause you to use a lot more throttle and the
    transmission may think you want to downshift. The easiest way to check that
    is to put a vacuum gauge on the intake manifold somewhere and see if the
    vacuum is up around 27 inches or so or down a lot lower. If it is real low,
    your cat is plugged.

    Tom
     
    Tom, Oct 12, 2007
    #4
  5. mdqcumber

    mdqcumber Guest

    Rob,

    It's a 2004 with a 2.7L V6 and automatic transmission.

    Tks, Mark
     
    mdqcumber, Oct 12, 2007
    #5
  6. mdqcumber

    mdqcumber Guest

    Mike,

    I had to scanned in Miami at the end of August (30th), which showed
    throttle position sensor was bad. It was replaced them and the throttle
    body was replaced about 3 weeks ago.

    I'm having scanned again this weekend, I'll update this on Saturday or
    Sunday.

    Tks, Mark
     
    mdqcumber, Oct 12, 2007
    #6
  7. mdqcumber

    mdqcumber Guest

    Tom,

    Thanks for the information. I'll have it scanned again this weekend
    and get the codes. I'll also research the Cat/Vacuum route.

    Tks, Mark
     
    mdqcumber, Oct 12, 2007
    #7
  8. mdqcumber

    Mike Marlow Guest

    Mark:

    Your comments are automatically posting to alt.autos.hyundai (usenet) and
    without you including the text that you are replying to it is difficult to
    figure out the context of your replies. Please include the text you are
    replying to so we can keep up with the conversation.
     
    Mike Marlow, Oct 12, 2007
    #8
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