Bucking when underload

Discussion in 'Mazdaspeed 3 Troubleshooting' started by Ms3.Owen, Mar 30, 2024.

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  1. Ms3.Owen

    Ms3.Owen Greenie Member

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    2010 mazdaspeed 3
    I’m trying to figure out why my car is bucking saw some thread with people having similar problems but never saw an answer. Sometimes while starting the car normally when it’s warm the idle is at 500rpm until I tap the gas after that it seems to be normal. Also when accelerating only seems to be when I’m more then 50% throttle the car bucks and what seems to me like misfires. I’ve done the test where you shut the car off while warm and check fuel pressure with your Cobb ap and it’s supposed to go up and then drop down but mine just drops down. I’ve had the problem a few months ago but replaced my spark plugs and it fixed it until a couple weeks ago but this time it seems worse. If anyone had this similar issue let me know what you did to solve it. Thanks in advance!
     
    Ms3.Owen, via an iPhone, Mar 30, 2024
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  2. Easter Bunny

    Easter Bunny Professional Engineer Motorhead Platinum Member

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    Check your spark plug gap.
     
    Easter Bunny, via a mobile device, Mar 30, 2024
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  3. Ms3.Owen

    Ms3.Owen Greenie Member

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    I gapped them when I replaced them a couple months ago they shouldn’t be bad this quick I’m guessing there’s a fuel issue cause if them to foul out
     
    Ms3.Owen, via an iPhone, Mar 30, 2024
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  4. Mtnbker3531

    Mtnbker3531 Platinum Member

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    So did you conduct the PRV test with a HOT motor. The test relies on the heat from the engine to cause the fuel pressure to rise.



    Also take a data log of this behavior while driving and see what your fuel pressure is doing. This potentially sounds like a bad PRV but it could be other things. Post that data log here if you want as well.

    Also can you look at the Troubleshooting sheet at the top of this section and include all that info here, it will help in trying to figure out what's going on.
     
    Mtnbker3531, via a mobile device, Mar 30, 2024
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  5. Raider

    Raider Administraider Administrator Platinum Member

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    Amazon coil packs or Amazon spark plugs?
     
    Raider, via an iPhone, Mar 30, 2024
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  6. Easter Bunny

    Easter Bunny Professional Engineer Motorhead Platinum Member

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    Seriously you are describing a misfire check the spark plug gap
     
    Easter Bunny, via a mobile device, Mar 30, 2024
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  7. Ms3.Owen

    Ms3.Owen Greenie Member

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    No ngk plugs which I gapped properly when installing a couple months ago car fixed this issue then it has come back recently
     
    Ms3.Owen, via an iPhone, Mar 30, 2024
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  8. Ms3.Owen

    Ms3.Owen Greenie Member

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    Yes I did it when motor was hot multiple times and watched this video over and over to make sure I was doing it correctly
     
    Ms3.Owen, via an iPhone, Mar 30, 2024
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  9. Mtnbker3531

    Mtnbker3531 Platinum Member

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    Which exact plug did you use and what gap?
     
    Mtnbker3531, via a mobile device, Mar 30, 2024
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  10. Ms3.Owen

    Ms3.Owen Greenie Member

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    One step colder ngk plugs from corksport gapped to 0.026 which I double checked myself. Plugs shouldn’t go bad that quickly without something else causing that problem
     
    Ms3.Owen, via an iPhone, Mar 30, 2024
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  11. Mtnbker3531

    Mtnbker3531 Platinum Member

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    Agreed your plugs "should" be fine. How many miles do you have on these plugs? Have you pulled them and checked the gap since youve started having this issue?

    Do us a favor and include all the info included in the Troubleshooting Sheet.

    What coil packs are on the car?
     
    Last edited: Mar 30, 2024
    Mtnbker3531, via a mobile device, Mar 30, 2024
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  12. Easter Bunny

    Easter Bunny Professional Engineer Motorhead Platinum Member

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    One step colder is too cold for street driven
     
    Easter Bunny, via a mobile device, Mar 30, 2024
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  13. Mtnbker3531

    Mtnbker3531 Platinum Member

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    My car is "street" driven.....;)
    Im interested what setup OP has though as far as mods/tune?
     
  14. Ms3.Owen

    Ms3.Owen Greenie Member

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    Dumped a bottle of fuel injector cleaner in the tank and two days later she’s running perfectly no more bucking at wot !!!
     
    Ms3.Owen, via an iPhone, Apr 3, 2024
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  15. Mtnbker3531

    Mtnbker3531 Platinum Member

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    Well I hope that works out for you long term. I wouldn't call this "fixed".

    Fuel injector cleaner doesn't actually do anything to clean the injectors in these cars. They need to be professionally cleaned and flow tested.

    Not exactly sure why this solution "worked" but I honestly won't be surprised if you are revising this issue.
     
    Mtnbker3531, via a mobile device, Apr 4, 2024
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  16. Ms3.Owen

    Ms3.Owen Greenie Member

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    I’m honestly not sure what happened to fix it I tried a few things a couple days ago I’ll see if it does it again today or tomorrow and update in here. It’s been rainy here for about the past month except for yesterday so it’s quite possible that has something to do with it
     
    Ms3.Owen, via an iPhone, Apr 4, 2024
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  17. Ms3.Owen

    Ms3.Owen Greenie Member

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    Forgot to mention these are what my plugs looked like when I pulled them
     

    Attached Files:

    Ms3.Owen, via an iPhone, Apr 5, 2024
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  18. Mtnbker3531

    Mtnbker3531 Platinum Member

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    Mtnbker3531, via a mobile device, Apr 5, 2024
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  19. Ms3.Owen

    Ms3.Owen Greenie Member

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    Sorry didn’t know where to find this I’ll fill it out now

    Year/Make/Model: 2010 mazdaspeed3
    Mileage: 250k km
    Location: Canada
    Concern: bucking under load (normally at wot or close to it)
    DTC's: P0455 (P0302-showed up after bucking but doesn’t stay) abs and traction control light (abs pump according to a scanner)
    Modifications
    Cork sport short ram intake
    Corksport Catless Downpipe
    Corksport Catless Race pipe
    Cobb boost controller
    GFB Bov
    Corksport intercooler piping (top mount)
    ECU/Tuning Software: Cobb ap V3
    Tuner: freeke tune
    Is the concern intermittent? Kinda
    Can you duplicate the concern? Yes
    Recent Repairs: nothing engine wise
    Correction:
     
    Last edited by a moderator: Apr 6, 2024
    Ms3.Owen, via an iPhone, Apr 5, 2024
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  20. Easter Bunny

    Easter Bunny Professional Engineer Motorhead Platinum Member

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    That second spark plug pic has a lot of oil on it....
     
    Easter Bunny, via a mobile device, Apr 5, 2024
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