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Discuss jerking and hesitation at low acceleration in the alt.autos.subaru forum at Car Dealer Forums; I have a 2000 OBW, 2.5L-5MT, approx. 180k km. Recently it's been exhibiting some wierd ...
  1. #1
    Yousuf Khan
    Guest

    Default jerking and hesitation at low acceleration

    I have a 2000 OBW, 2.5L-5MT, approx. 180k km. Recently it's been
    exhibiting some wierd jerking and hesitation behaviour. It seems to
    occur mainly under slow acceleration or cruise control mode. If I'm
    slowing down, a slow steady release of the throttle would at some point
    produce a hesitating jerk. When accelerating, if I'm accelerating
    slowly, it would also jerk. If I'm giving it some heavy gas, then there
    would be no problem.

    It also happens while in cruise mode. It seems that slight changes in
    throttle position create disproportionately large acceleration or
    deceleration. What could be the cause of this, throttle position sensor,
    fuel, spark, etc.?

    Yousuf Khan



    › See More: jerking and hesitation at low acceleration

  2. #2
    Todd H.
    Guest

    Default Re: jerking and hesitation at low acceleration

    Yousuf Khan <bbbl67@yahoo.com> writes:

    > I have a 2000 OBW, 2.5L-5MT, approx. 180k km. Recently it's been
    > exhibiting some wierd jerking and hesitation behaviour. It seems to
    > occur mainly under slow acceleration or cruise control mode. If I'm
    > slowing down, a slow steady release of the throttle would at some
    > point produce a hesitating jerk. When accelerating, if I'm
    > accelerating slowly, it would also jerk. If I'm giving it some heavy
    > gas, then there would be no problem.
    >
    > It also happens while in cruise mode. It seems that slight changes in
    > throttle position create disproportionately large acceleration or
    > deceleration. What could be the cause of this, throttle position
    > sensor, fuel, spark, etc.?


    Curious, did some numbnuts recently change your timing belt? Tensioner?


    I had these symptoms and over teh course of 9 months having gone
    through changing plug wires, cam sensors, crank sensors, o2 sensors,
    having the head rebuilt and the problem persisted.

    Turned out to correlate back to a timing belt change with a new subaru
    tensioner, and the belt jumping one tooth intermittently.

    Getting any check engine lights/codes? In my case the subtle annoying
    crap yer talking about happened for a long long time before the car
    would finally throw a code, usually misfire on a cylinder or 4, or
    something pionting to crank or cam sensors. All leading one on a
    wild goose chase.


    --
    Todd H.
    2001 Legacy Outback Wagon, 2.5L H-4
    Chicago, Illinois USA

  3. #3
    dnoyeB
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Thu, 12 Jun 2008 23:33:01 -0400, Yousuf Khan wrote:

    > I have a 2000 OBW, 2.5L-5MT, approx. 180k km. Recently it's been
    > exhibiting some wierd jerking and hesitation behaviour. It seems to
    > occur mainly under slow acceleration or cruise control mode. If I'm
    > slowing down, a slow steady release of the throttle would at some point
    > produce a hesitating jerk. When accelerating, if I'm accelerating
    > slowly, it would also jerk. If I'm giving it some heavy gas, then there
    > would be no problem.
    >
    > It also happens while in cruise mode. It seems that slight changes in
    > throttle position create disproportionately large acceleration or
    > deceleration. What could be the cause of this, throttle position sensor,
    > fuel, spark, etc.?
    >
    > Yousuf Khan


    sounds like a problem with the ignition system. I would start by looking
    at spark plug wires, then plugs themselves, then the ignition coils. If
    those are all good, then check the timing belt.

    If all that is good, then start looking at the gas system like the fuel
    pump/filter though its a bit soon for that.

  4. #4
    Dan
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Jun 12, 8:33*pm, Yousuf Khan <bbb...@yahoo.com> wrote:
    > I have a 2000 OBW, 2.5L-5MT, approx. 180k km. Recently it's been
    > exhibiting some wierd jerking and hesitation behaviour. It seems to
    > occur mainly under slow acceleration or cruise control mode. If I'm
    > slowing down, a slow steady release of the throttle would at some point
    > produce a hesitating jerk. When accelerating, if I'm accelerating
    > slowly, it would also jerk. If I'm giving it some heavy gas, then there
    > would be no problem.
    >
    > It also happens while in cruise mode. It seems that slight changes in
    > throttle position create disproportionately large acceleration or
    > deceleration. What could be the cause of this, throttle position sensor,
    > fuel, spark, etc.?
    >
    > * * * * Yousuf Khan


    I had similar problems with 94 Legacy and turned out to be a small
    pinhole burned into one of the spark plug insulator boots. Good luck.

  5. #5
    YKhan
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Jun 13, 9:33 am, dnoyeB <as...@fake.net> wrote:
    > sounds like a problem with the ignition system. I would start by looking
    > at spark plug wires, then plugs themselves, then the ignition coils. If
    > those are all good, then check the timing belt.


    All of the sparkplug wires were changed a little over a year ago, when
    I noticed a hesitancy early in the morning when first starting the car
    up. Turned out that there were holes in the wire which were causing
    short circuits when early morning moisture coated them. However, the
    timing belt might be something to look into, as I was told during a
    recent oil change that the belts were getting frayed.

    Yousuf Khan

  6. #6
    YKhan
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Jun 13, 1:25 am, sub...@toddh.net (Todd H.) wrote:
    > Curious, did some numbnuts recently change your timing belt? Tensioner?
    >
    > I had these symptoms and over teh course of 9 months having gone
    > through changing plug wires, cam sensors, crank sensors, o2 sensors,
    > having the head rebuilt and the problem persisted.
    >
    > Turned out to correlate back to a timing belt change with a new subaru
    > tensioner, and the belt jumping one tooth intermittently.


    No, I haven't had any numbnuts changing my timing belt yet. :-)

    However, now that you mention timing belt, I remember I was told by
    some techs at Mr. Lube, where I get my oil changed that they noticed
    that the timing belt was getting frayed. I normally don't trust them
    with anything other than oil changes, so I semi-ignored them.

    > Getting any check engine lights/codes? In my case the subtle annoying
    > crap yer talking about happened for a long long time before the car
    > would finally throw a code, usually misfire on a cylinder or 4, or
    > something pionting to crank or cam sensors. All leading one on a
    > wild goose chase.


    No, there's no check engine warning yet.

  7. #7
    dnoyeB
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Sat, 14 Jun 2008 11:43:21 -0700, YKhan wrote:

    > On Jun 13, 9:33 am, dnoyeB <as...@fake.net> wrote:
    >> sounds like a problem with the ignition system. I would start by
    >> looking at spark plug wires, then plugs themselves, then the ignition
    >> coils. If those are all good, then check the timing belt.

    >
    > All of the sparkplug wires were changed a little over a year ago, when I
    > noticed a hesitancy early in the morning when first starting the car up.
    > Turned out that there were holes in the wire which were causing short
    > circuits when early morning moisture coated them. However, the timing
    > belt might be something to look into, as I was told during a recent oil
    > change that the belts were getting frayed.
    >
    > Yousuf Khan


    How well does it shift, or is this a manual?

    I would look at fuel before timing to be honest. especially since it is
    not a continuous problem. Does the car run any hotter?

  8. #8
    dnoyeB
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Sat, 14 Jun 2008 11:10:46 -0700, Dan wrote:

    > On Jun 12, 8:33*pm, Yousuf Khan <bbb...@yahoo.com> wrote:
    >> I have a 2000 OBW, 2.5L-5MT, approx. 180k km. Recently it's been
    >> exhibiting some wierd jerking and hesitation behaviour. It seems to
    >> occur mainly under slow acceleration or cruise control mode. If I'm
    >> slowing down, a slow steady release of the throttle would at some point
    >> produce a hesitating jerk. When accelerating, if I'm accelerating
    >> slowly, it would also jerk. If I'm giving it some heavy gas, then there
    >> would be no problem.
    >>
    >> It also happens while in cruise mode. It seems that slight changes in
    >> throttle position create disproportionately large acceleration or
    >> deceleration. What could be the cause of this, throttle position
    >> sensor, fuel, spark, etc.?
    >>
    >> * * * * Yousuf Khan

    >
    > I had similar problems with 94 Legacy and turned out to be a small
    > pinhole burned into one of the spark plug insulator boots. Good luck.


    This is why I hang on to my old timing light. You can put the light on
    each wire as close to the plug as possible, and look at the flashes and
    see if there are any misses. Lets you know the cables are bad right away.

    Of course it wouldn't catch a boot problem.

  9. #9
    clare at snyder dot ontario dot canada
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Sat, 14 Jun 2008 19:01:43 -0500, dnoyeB <askme@fake.net> wrote:

    >On Sat, 14 Jun 2008 11:43:21 -0700, YKhan wrote:
    >
    >> On Jun 13, 9:33 am, dnoyeB <as...@fake.net> wrote:
    >>> sounds like a problem with the ignition system. I would start by
    >>> looking at spark plug wires, then plugs themselves, then the ignition
    >>> coils. If those are all good, then check the timing belt.

    >>
    >> All of the sparkplug wires were changed a little over a year ago, when I
    >> noticed a hesitancy early in the morning when first starting the car up.
    >> Turned out that there were holes in the wire which were causing short
    >> circuits when early morning moisture coated them. However, the timing
    >> belt might be something to look into, as I was told during a recent oil
    >> change that the belts were getting frayed.
    >>
    >> Yousuf Khan

    >
    >How well does it shift, or is this a manual?
    >
    >I would look at fuel before timing to be honest. especially since it is
    >not a continuous problem. Does the car run any hotter?

    Also, what plugs were put in a year ago. If they were Bosch Platinums,
    pull them out and throw them as far as you can. Put in the recommended
    NGK or Nippondenso plugs. I have had that kind of trouble with just
    about every set of Bosch platinums I've ever run across.
    ** Posted from http://www.teranews.com **

  10. #10
    dnoyeB
    Guest

    Default Re: jerking and hesitation at low acceleration

    On Sun, 15 Jun 2008 14:54:59 +1200, Bugalugs wrote:

    > YKhan wrote:
    >> On Jun 13, 9:33 am, dnoyeB <as...@fake.net> wrote:
    >>> sounds like a problem with the ignition system. I would start by
    >>> looking at spark plug wires, then plugs themselves, then the ignition
    >>> coils. If those are all good, then check the timing belt.

    >>
    >> All of the sparkplug wires were changed a little over a year ago, when
    >> I noticed a hesitancy early in the morning when first starting the car
    >> up. Turned out that there were holes in the wire which were causing
    >> short circuits when early morning moisture coated them. However, the
    >> timing belt might be something to look into, as I was told during a
    >> recent oil change that the belts were getting frayed.
    >>

    > I would treat that information with a pinch of salt The timing belt
    > is enclosed and there is no way of seeing "that the belts were getting
    > frayed" without removing the covers. There is no need to remove those
    > covers when changing the oil.


    I assumed he meant the belts he could see were worn. But true enough my
    visible belts were work and I replaced them all. Then I opened up my
    timing belt cover and that belt was fine..


    CL

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