RPM and Speed bounce/boggles

Discussion in 'Mazdaspeed 3 Troubleshooting' started by Ms3orDie, Mar 10, 2021.

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  1. Ms3orDie

    Ms3orDie Greenie Member

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    unfortunately im not having any luck.
     
    Ms3orDie, via an iPhone, Apr 6, 2021
    #21
  2. The_big_dill

    The_big_dill Greenie Member

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    What was the last thing you did on your car prior to this problem?

    From your log, my observations tell me your ECU is pulling a ton of fuel and your system is reporting extremely rich when you let off the gas. Your system is responding to it, but the readings are extreme for the conditions.

    Typically this would exhibit a boost leak, but the problem seems to exist in vacuum conditions.

    Have a look at this snippet from your log:
    upload_2021-4-20_22-33-27.png

    The key here is to remember that you have a steady throttle position and APP, steady vacuum/boost, steady fuel pressure. However, if you look at your AFR, it is jumping from 12 to 26 to 9 in a matter of milliseconds and eventually recovers closer to what it should be under these conditions (~stoich).

    You can confirm that your system is appropriately compensating for that with the fuel trims, when the AFR jumps around, so do your short trims.

    My next diagnosis would be based on changes on your car. But to me this looks like an intermittent sensor malfunction, potentially due to damaged wiring or a malfunctioning sensor. My guess would be your O2 sensor with the information I have.

    Do you have a full throttle (WOT) log?
     
    Last edited: Apr 20, 2021
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  3. Awafrican

    Awafrican Moderator Gold Member

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    When you installed the Damond PMM and relocated the ground wire is that making good contact? Could throw some weird stuff, don't think it's "the issue" but worth a look that and as always the ground by the hpfp.
     
    Awafrican, via a mobile device, Apr 20, 2021
    #23
  4. Sho

    Sho Silver Member

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    Do you have a VTA BOV? If so, the spring inside is too weak. If adjustable, you need to turn it to tighter setting. If not, stiffer spring.

    For example. I run a tial Q 50mm valve with a -12psi spring. I run that particular spring as my car idles at -10.5psi and pulls -11.9xpsi vac during engine braking.

    A weaker spring such as the -10 exhibits the same symptoms youre having
     
    Sho, via a mobile device, Apr 21, 2021
    #24
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  5. Easter Bunny

    Easter Bunny Professional Engineer Motorhead Platinum Member

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    All i read was blue two shims
     
    Easter Bunny, via a mobile device, Apr 21, 2021
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