hesitation under full throttle need some help
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This is a discussion on hesitation under full throttle need some help within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; hey everyone hope all of you are well today^_^ my issue is that under full boost my car hesitates at ...

  1. #1
    Registered User kornkid21792's Avatar
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    hesitation under full throttle need some help

    hey everyone hope all of you are well today^_^
    my issue is that under full boost my car hesitates at around 4000 rpm under full throttle.if i keep the peddle pressed down it will hesitate then accelerate then hesitate again and it will do that till red line.

    under normal driving conditions or slight acceleration there is no issues at all and the car is perfectly normal,the only time it starts to act up is under full boost.

    i pulled out the plugs and checked them,they are ngk 1 step colder copper plugs and they looked fine,they have only been in there for about 7000 miles.
    coil pack and connectors looked good as well.

    i cleaned the mass air flow sensor,i checked for boost leaks which there was none.the car is not running lean under full boost when it hesitates,i have verified that by looking at my wide-band.it is also not over boosting.i also switched out the maf from another car that was running fine.

    no cel, the front afr sensor,the oem one, has about 90,000 miles on it,the fuel filter is at about 10,000.i also checked my feedback knock and fine knock tables and nothing is showing up there either,dam is still currently at 16 as well.

    checked the fuel pressure just turning the ignition to on it went to 35 and with the car on it idle at 40,i did this test on the fuel filter outlet side.
    and with the the fuel pressure regulator vac line off.turning ignition on fuel pressure wast at 0 and then at idle it was at 45

    the only thing i can really think of is the spark plugs can they be bad even though they look fine,but they looked fine to me,and i don't know why they would just start causing problems now,all of sudden,but this is just a thought.please let me know if you have any ideas

    i am pro tuned and my engine mods are
    turbo xs tmic
    vf39 turbo
    cnt downpipe
    turbo back exhaust
    sti uppipe
    grimmspeed crank pulley
    deatschwerks 565cc spec c injectors
    deatschwerks 301 fuel pump
    cobb intake
    cobb maf hose
    borla header
    perrin turbo inlet
    perrin turbo blanket
    perrin ebcs
    k&n air filter
    innovate wideband
    prosport boost gauge

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  3. #2
    He simply abides. SD_GR's Avatar
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    hesitation under full throttle need some help

    No CEL and no overboosting confuses me. Id have said fuel cut but not like this so I don't know. Consider real time data; maybe a passenger connected via OBD2 might tell you more.
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    Registered User kornkid21792's Avatar
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    haha it confuses me to! we checked real time data did a datalog and looking at the log everything looks normal,the log would have you think its not even happening.
    i check the coil packs the only thing i can think of is maybe the spark plugs are bad even though they look fine
    have you heard of that before?

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    Master Baiter EJ257's Avatar
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    Re: hesitation under full throttle need some help

    What do you have in your log?
    2005 WRX STi (Mods | Virtual Dyno)

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  6. #5
    Registered User kornkid21792's Avatar
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    everything looks fine in log,its at home but i can put up here when i get back.

    also my wideband is reading 10.1 at full throttle

  7. #6
    Registered User Ruh Roh's Avatar
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    clutch slipping?

  8. #7
    Registered User kornkid21792's Avatar
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    good idea but no,its defiantly not a clutch slip you can hear it cut out when it hesitates

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by kornkid21792
    also my wideband is reading 10.1 at full throttle
    Is that what you want it to read? When was the last time you did a calibration on it?
    2005 WRX STi (Mods | Virtual Dyno)

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  10. #9
    Registered User nsibanez's Avatar
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    have you tried something as simple like cleaning out your throttle body? i dont know if that would fix it from accelerating, hesitating, then accelerating again though

  11. #10
    Moderator Donkey's Avatar
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    What vehicle is this? You listed your mods but not the vehicle. And post a datalog. Did you check the gap on the plugs? Copper plugs are only good for about 15K-20K miles before they need to be replaced/regapped.
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    Sounds like spark plug wires. Does it backfire ?

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    Moderator Donkey's Avatar
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    Quote Originally Posted by K4RT8OY View Post
    Sounds like spark plug wires. Does it backfire ?
    There are no sparkplug wires on ANY USDM WRX or STI.............
    Resident Adviser @ WTF Tuning, LLC
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    Quote Originally Posted by Donkey View Post
    There are no sparkplug wires on ANY USDM WRX or STI.............
    Ok, then i quess you call it the Coilpack connectors

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    Luke Skywalker Mikie13's Avatar
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    I got money on a Boost leak.
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  16. #15
    Registered User kornkid21792's Avatar
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    Quote Originally Posted by Donkey View Post
    What vehicle is this? You listed your mods but not the vehicle. And post a datalog. Did you check the gap on the plugs? Copper plugs are only good for about 15K-20K miles before they need to be replaced/regapped.
    hey sorry i didnt respond quicker work is nuts!
    i replaced the plugs with some stock heat range plugs and now the problem is completely gone-_- maybe i got a bad batch of plugs or something who knows,i just thought id let you all know its fixed!
    also the plugs only had like 7000.
    thank you everyone for your contributions, and the brainstorming i appreciate you all very much!

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