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Shudder when coming to a stop.

Discussion in 'VT - VX Holden Commodore (1997 - 2002)' started by accentstencil, Sep 18, 2014.

  1. accentstencil

    accentstencil Well-Known Member

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    It is not a wheel shudder but and engine shudder, it happens when I am coming to a complete stop, like at traffic lights.
    It's been happening for years and is getting worse with time and it's driving me crazy.
    It is not the engine or transmission as they have both been reconditioned and it was doing it before these were fixed.
    Could it be brake booster related? No problem with brakes, they work great.
    Anyone had a similar problem?
     
  2. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    Assuming it's auto, was the torque converter done as well?

    Possibly a diff or drive line issue transferring back through the transmission/engine?
     
  3. accentstencil

    accentstencil Well-Known Member

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    Not sure about the torque converter, had it done by a reputable transmission specialist.
    Don't think it is a diff or drive line issue as it happens as I come to a complete stop and the car has stopped moving. Just as the car stops.
    I also get a similar shudder when the engine fans kick in.
     
  4. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    Well then it's an IAC issue. As you come to a stop the IAC is settling the idle, same when the thermo fan kicks in. The IAC might be letting the idle drop a little low.

    You're not my chance running a 20% under driven balancer?
     
  5. accentstencil

    accentstencil Well-Known Member

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    That sounds feasible, I will look into the IAC. I was going to change it a while back just in case but the LS1 IAC is about tripple the price of the V6 IAC, but I will bite the bullet and give it a go.

    "You're not my chance running a 20% under driven balancer?" I don't know what that is so I guess not.
     
  6. SavVYute

    SavVYute Active Member

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    Before you go spending money replacing anything look into cleaning any valves that close when you drop down to idle.
    The IAC gets carboned up and might be sticking and the airway leading to it can get pretty dirty.
    The EGR valve also gets a build up of carbon around it too. Careful cleaning of that could help.
    And your PCV could be chocka with crud too.
     
  7. accentstencil

    accentstencil Well-Known Member

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    Cleaned IAC several times, replaced entire PCV twice. Will check the EGR valve.
    I'm tending to agree with immortality, the IAC might be a bit slow in settling at the idle speed. It has not been changed in 12 years so it might be time.
     
  8. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    LS motors have a reputation for breathing heavily. Maybe like the V6's, try cleaning the TB and IAC first.

    A under driven harmonic balancer reduces parasitic losses by turning the engine accessories at a slower speed. Sometimes this causes poor charging at idle because the alternator is turning to slow although I've only really heard of it occurring on some V6's.

    edit:lol a bit slow to post.....
     
  9. Jake96

    Jake96 Member

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    How’d you go figuring out the problem mate? I got a 08 v6 ve and since I’ve had it i can feel slight shuddering on the brake pedal when sitting at a set of lights. Took it to a mechanic replaced spark plugs and engine mounts went away for a week and came back again? And now when I go to slow down when I get to about 7kph the car shudders and has constant shuddering on the brake pedal. Any ideas? I’ve cleaned the throttle body/maf sensor and a mechanic checked for air leaks and checked the brake booster it has him stumped for what it is.
     
  10. accentstencil

    accentstencil Well-Known Member

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    I don't feel the shudder through the brake pedal so probably a different issue. Maybe check the engine mounts.
    I just noticed that this thread is three years old and the car is still doing it. Changed IAC and TPS this week and at first I thought it was fixed but that was short lived. I have noticed that the quicker I come to a stop the worse it is. If I pull up slowly like an old lady there is no shudder.
     
  11. devilly

    devilly Guest

    02 sensors something electrical as it can't be driveline if doing it when stationery can't be brakes or rotors. have you checked the brake booster rubber and the check value. I used a heap of gasket goo around the rubber on the check value. Egr also springs to mind maybe give it a few hard revs to clean it all out. injector cleaner and run it at high revs for a bit could just be stuff that needs a few hard revs to remove. how does it idle if you remove the iac plug then the tps plug. you could also check the l/h. maybe post a video hope you find it and get it sorted out.
     
  12. accentstencil

    accentstencil Well-Known Member

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    I also thought of the check valve and grommet as it felt a bit loose, replaced both items two weeks ago.
    Replaced both O2 sensors about three years ago, about a month before I posted this thread so the problem was still there with new sensors.
    I put in reconditioned engine about six months before that so it should be nothing to do with with the engine internals.
    Each time I replace something or do some maintenance I'm hoping to strike it lucky.
    It's not a major issue, just one of those annoying things.
     
  13. devilly

    devilly Guest

    some ideas on what to check if haven't already. what about gearbox mount, accelerator cable adjustment, knock sensors. vacuum leak or even cracked headers which is slowly getting bigger so the problem is getting a bit worse.my mind keeps telling me shudder is normal uni joints or diff U shape rubber housing thingo. I hate little problems I know with my luck it turns into something bad lol :) I hope you find it before its a bigger problem. I dunno your motor could it be as easy as a tune. thinking old school of timing light and points here and dizzy they would shudder and engine if not set properly. I have a brain ach now lol :) coffee time.
     
  14. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    Not 100% on the LS TB adjustment but try opening the butterfly a touch using the butterfly stop screw that way the IAC has has to open less to maintain the idle and the idle rpm is less likely to drop to far. I'd try 1/2 a turn and see what it does that way if it doesn't work it's easy enough to adjust back to the original setting.
     
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  15. accentstencil

    accentstencil Well-Known Member

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    Transmission mount replaced about a year ago.
    Throttle cable can't really be adjusted.
    I'm thinking IAC is slow to respond, could be an issue with the PCM
     
  16. accentstencil

    accentstencil Well-Known Member

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    I didn't know there was an adjustment screw, it was well hidden and very difficult to access.
    I adjusted it to raise the idle by about 100 RPM and the shudder when stopping has gone.
    I am going to adjust it back and try the 40 minute IDLE LEARN PROCEDURE and see how that goes, if that doesn't help I will turn the adjustment screw up again.
    https://forums.justcommodores.com.au/threads/idle-learn-procedure.267669/
     
  17. devilly

    devilly Guest

    awesome news, sounds like your on to something, hope it fixes it
     
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  18. Christophoon

    Christophoon New Member

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    how did you go? my VF Evoke may be having a similar issue, did the Idle Re-Learn work out?
     
  19. accentstencil

    accentstencil Well-Known Member

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    The problem still exists, with all things that have been replaced over the years I thought one of them might have fixed the problem. I think the idle re-learn did help for a little while. The shudder is particularly bad when I first turn on the A/C but seems to improve after driving for a while.
     
  20. Christophoon

    Christophoon New Member

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    Did you end up cleaning the IAC? or any of the idle controllers?
     

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