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Thread: massive hesitation when accelerating.

  1. #1
    JZ Powered Too Much Toyota EldarO's Avatar
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    Default massive hesitation when accelerating.

    hey all, this is on my sierra but same diff.

    i go to take off, or floor it (while already moving) and the car will bog down, and i mean bog down, to the point of where it will nearly stall.

    then, it'll pick up a bit, and struggle cough and splutter, till i floor it, and it picks up its revs, then goes like the clappers.

    if i then slow down, then speed up suddenly, it doesnt bog, however if i slow down, then cruise along at that same speed, then floor it, it will bog.

    frankly im at a loss as to what it is, and its been getting progressively worse.

    it nearly killed me today when i bogged down, turning onto a road, with a semi coming the other way.

    motor is a fresh reco, as is carbie, however parts of the carby arent new, as the carby i bought was a newer model, and a few things needed to be swapped onto mine to make it work.

    its alot worse when its cold (it will actually stall) and when warm its usually bearable.

    any ideas?

    it was fine, ive changed nothing, and it started, then got alot worse, so its not my tinkering.

    accel pump or somesuch poop?

  2. #2
    Junior Member Domestic Engineer
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    Default Re: massive hesitation when accelerating.

    sounds like overfueling!

    as you cruise, it floods the carby, once you open it up, it skulls petrol(bogging), slowly it returns to a stoichometric mixture, as the carby empties its over-filled chamber(forgot the word) it starts to make power thus goin hard. Then wen you start cruising again, it starts flooding slowly, and thus the cycle continues!

    Just like tuning a 2-stroker nitro motor!!

    or maybe im just talking crap! maybe the seat and needle seals, since it was reco'd! Jets too big on new carby!

    hope that helps ya a bit!
    wog
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  3. #3
    3RZFE-T Backyard Mechanic
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    Default Re: massive hesitation when accelerating.

    Its deff a Fuel issue.
    Iam thinking over fueling as stated above. Maybe the wrong needle has been fitted. But it cant be as it has been a progressive issue. Geeze You got a sneaky gremlin.

    Does it have the old Wax choke like the 22y engines.

  4. #4
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: massive hesitation when accelerating.

    Quote Originally Posted by EldarO
    its alot worse when its cold (it will actually stall) and when warm its usually bearable.
    when cold, fuel drops out of the air stream and the mixture goes leaner.

    if your problem is worse when cold, then it is running lean... methinks.

    can you richen up the idle jet a turn and see if it has any effect?

    didn7t happen to reseal the carby using silicon at all?
    "I'm a Teaspoon, not a mechanic"
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  5. #5
    Junior Member Domestic Engineer
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    Default Re: massive hesitation when accelerating.

    Quote Originally Posted by oldcorollas
    when cold, fuel drops out of the air stream and the mixture goes leaner.

    if your problem is worse when cold, then it is running lean... methinks.

    can you richen up the idle jet a turn and see if it has any effect?

    didn7t happen to reseal the carby using silicon at all?

    Doesnt bogging down usually indicate rich mixtures though?
    Current: 94 jzs147 aristo, 92 ep82gt starlet
    Prev: ma61, gz20, jza70, uzz31, ncp10r, 92 sw20r
    And the winner of the big car race is......HOT ROD ZOIDBERG!

  6. #6
    Junior Member Domestic Engineer
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    Default Re: massive hesitation when accelerating.

    bad seals somewhere, would xplain the progression! fuel degrades the seals, get worse and worse over time, thus running more like cr#p!

    you have an interesting issue i must say!
    Current: 94 jzs147 aristo, 92 ep82gt starlet
    Prev: ma61, gz20, jza70, uzz31, ncp10r, 92 sw20r
    And the winner of the big car race is......HOT ROD ZOIDBERG!

  7. #7
    Fuel Economy Warrior Carport Converter Vios-GT_07's Avatar
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    Default Re: massive hesitation when accelerating.

    also could be the float is sticking or the bowl is over-fueling or not filling enough..

    if the plugs indicate a lean mix, it could be a failing fuel pump?
    Research has shown child in front seat causes accidents, accident in back seat causes child

  8. #8
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: massive hesitation when accelerating.

    Quote Originally Posted by woggin
    Doesnt bogging down usually indicate rich mixtures though?
    it can be either rich or lean.

    if it is rich and worse when cold, what do you think is causing it?
    could be choke...

    could just be an incorrectly assembled carby
    "I'm a Teaspoon, not a mechanic"
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  9. #9
    Junior Member Domestic Engineer
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    Default Re: massive hesitation when accelerating.

    Oh yea, forgot they had chokes! maybe i should just stick to efi!
    Current: 94 jzs147 aristo, 92 ep82gt starlet
    Prev: ma61, gz20, jza70, uzz31, ncp10r, 92 sw20r
    And the winner of the big car race is......HOT ROD ZOIDBERG!

  10. #10
    Junior Member Automotive Encyclopaedia
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    Default Re: massive hesitation when accelerating.

    Sounds like the acc. pump or a secondary barrel opening up too soon, or the choke swinging closed
    Does it help or hurt if the throttle is pumped when this is happening?

    Look in the carb, twist the throttle, see & hear a jet of fuel from the acc. pump of about 2cc. On many there isn't even a need to remove the air cleaner because it's loud enough to hear.
    'I've scrapped better.' John stated when asked about the car by the guy with the silver tipped cowboy boots!

  11. #11
    JoeyJoeJoeJuniorShabadoo Domestic Engineer joey's Avatar
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    Default Re: massive hesitation when accelerating.

    Check plugs to see if they are fouled or not. Dark black plugs indicate running rich. May help you in some way.
    Mr Shabadoo.
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  12. #12
    JZ Powered Too Much Toyota EldarO's Avatar
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    Default Re: massive hesitation when accelerating.

    carby is a few weeks old, and i only ever run premium 98.

    ill rip apart the carb tomorrow and check if anything is out of whack, but i just dont know what im looking at, or for.

  13. #13
    Im a hopeless Domestic Engineer
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    Default Re: massive hesitation when accelerating.

    try running 95.. it may actually run better if its currently rich

    when you drop the boot on her it may just be dumping a heap of fuel in it, does it bog down if you progressively apply throttle before opening it all the way?
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  14. #14
    Forum Member 1st year Apprentice
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    Default Re: massive hesitation when accelerating.

    Exact same problem with my 5k. My technical diagnosis was 'its farked and needs a repower' but the above suggestions are far more concise.
    1985 KP60 Starlet - Sold
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  15. #15
    Slanted Photographer Automotive Encyclopaedia LeaThaL's Avatar
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    Default Re: massive hesitation when accelerating.

    or you have really bad gap on your plugs, i had this in my 3sfe ST184, replaced the plugs and it was fine after that but yeah
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