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Thread: Miata dead. need some help

  1. #1
    6,000 rpm - mere mortals would shift Demon I Am's Avatar
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    Miata dead. need some help

    On the cell, so excuse any misspellings.

    Car started bucking/losing power. Pulled into gas station and refilled, checked oil and obd2.
    Code p0420.
    Left the car parked for 8 hours. Came back to it.
    When running sounded like a tractor.
    Smoke white coming from rear of motor.
    Car drove like shit, to speed maybe 30 with the pedal down. Had to move it from where it was parked.
    Checked obd2
    P0420
    P0300
    Barely idles

  2. #2
    Super Moderator tsingson's Avatar
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    From what I was reading, the P0420 is O2 sensor. Are you getting a steady misfire?

  3. #3
    3,000 rpm - starting to feel the power BoBo's Avatar
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    It might be Cat converter or 02 sensor related on (bank1) according to the link I posted.Sucks, a P0300 doesn't tell you specifically which cylinder(s) is/are misfiring, nor why. A buddy of mine had a similar problem he ended up buying another miata since the motor was already 250k+.

    According to p0420.com,

    "There are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly. The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc".

    For more info:http://www.p0420.com/

    I hope you get your Roadster back on the road.
    Last edited by BoBo; 05-23-2015 at 08:31 PM.
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    Forum Sponsor revlimiter's Avatar
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    I wonder if it could be a plugged cat or exhaust? Just pulling at straws here.

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    Ninja Messiah kung fu jesus's Avatar
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    Tony,

    List of things to check:

    Resistance on the coils
    Crank position sensor (dirt/crud build up on the sensor and or plate on crank pulley)
    Cam position sensor
    Plugs/wires
    Loose/frayed broken wires

    When the timing goes bad, the O2 starts freaking out.

    Another avenue, if you had surging, can be a dirty IAC valve and throttle body.

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  8. #6
    6,000 rpm - mere mortals would shift Demon I Am's Avatar
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    Ok, I'm going to look at the car again today. Need to tow it from Apex to Raleigh first.
    I've had the p0420 for a while, off and on. I believe it might be related to the EGR valve needing a good clean-out. When that code popped up previously, I just reset it and it stayed off until yesterday.

    I was told by another friend that the coil packs are notorious for failing on 99-00 Miata. I'll pull the plugs and check for spark. Hopefully this is the case, and I didn't fuck anything up by driving on few cylinders.

    I'll start with the easy to look at stuff, coils, wires, check oil for gas, check coolant for oil, CPS, etc and go from there.

    Of course this happens as soon as I sell my secondary car...

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    Supporting Member Grip Driver's Avatar
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    I'm with Adam, plugged cat or exhaust. Remove the front o2 and see if it runs any better.

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  11. #8
    4,000 rpm - entering the fun zone ScratchNSniff's Avatar
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    Hasn't happened to me on a Miata yet, but has on a few of the Proteges with the cat plugged and same symptoms...

  12. #9
    4,000 rpm - entering the fun zone Hyper's Avatar
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    Quote Originally Posted by kung fu jesus View Post
    Tony,

    List of things to check:

    Resistance on the coils
    Crank position sensor (dirt/crud build up on the sensor and or plate on crank pulley)
    Cam position sensor
    Plugs/wires
    Loose/frayed broken wires

    When the timing goes bad, the O2 starts freaking out.

    Another avenue, if you had surging, can be a dirty IAC valve and throttle body.
    listen to this guy, he is right in all points.

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  14. #10
    6,000 rpm - mere mortals would shift Demon I Am's Avatar
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    Barely had enough power to get it on the auto hauler. Got it back to Raleigh. Cranked it to roll of the trailer and it drove fine. I'll start looking at it after some food, and when the sun drops a little

  15. #11
    3,000 rpm - starting to feel the power JLBMX5's Avatar
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    My son bought me a huge canopy for Christmas i can loan you if you think you would need it Tony.

  16. #12
    Individual-1 ☚ ☻ ☛ Agent☣Orange's Avatar
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    Good advice here. I've worked on a couple that were completely dead and it was because they had replaced the crank sensor and didn't tuck away the wiring well enough and a belt ate through the wiring insulation and killed the sensor. If the car is still running, it isn't because of the crank sensor because it just won't run at all in that case, same with the cam sensor. My first guess is also a bad cat and a cat can go bad from a bad EGR or O2 sensor. IAC is a possiblity but it's a reach IMO.

    Sorry but I'm not on top of everyone's latest Miata but your info mentions a '90 Miata which you can't be reading any OBD-II info from so what are you driving now?


    No todo que es oro brilla.

  17. #13
    Super Moderator tsingson's Avatar
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    2000 NB

  18. #14
    Individual-1 ☚ ☻ ☛ Agent☣Orange's Avatar
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    NB1? Uff, coil pack... Wire gets loose inside the connector on top of the coil and causes misfires.


    No todo que es oro brilla.

  19. #15
    3,000 rpm - starting to feel the power Tkblazer's Avatar
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    ^ that would be my guess

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