P2138, won’t rev above 3000 rpms, lots of smoke

Discussion in 'Mazdaspeed 3/6 Engine' started by jsilva, Apr 12, 2020.

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  1. The_big_dill

    The_big_dill Greenie Member

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    I did a quick google search for mazdaspeed and P2138: https://www.mazda3forums.com/threads/my-speed-wont-drive.275472/
     
  2. jsilva

    jsilva Silver Member

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    jsilva, via an iPhone, Jun 17, 2020
    #62
  3. jsilva

    jsilva Silver Member

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    Ok ...

    I fiddled with the connector—I partially took it apart, pushed the wires in from behind, made sure the connecting thingies weren’t too big to make solid contact with the throttle body pins, etc. Things that seemed useless :)

    Then I tested the 2A pin on the PCM and it was working. So then I started it and it was working :)

    Still lots of smoke for a little while but it settled down and is now running like it did before this insane issue that was fixed by fiddling with a connector...!

    Still lots to do on the car—replace turbo and transmission, and I have a cylinder #4 misfire due to low compression (and actually I’m getting a new problem ... backfires)—but I’m glad to have it running again.

    Thanks very much to those who contributed and to Big Dill!
     
    Last edited: Jun 18, 2020
    jsilva, via an iPhone, Jun 18, 2020
    #63
  4. The_big_dill

    The_big_dill Greenie Member

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    Perseverance is key. Glad you got it figured out.

    Now get a replacement connector before this problem occurs again.

    Replace your spark plugs.

    Backfires are likely due to the amount of fuel you were dumping in the exhaust when cranking.

    Was the #4 missfire there before this ordeal?
     
  5. jsilva

    jsilva Silver Member

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    Yes, I will order another connector :)

    I think I’ll wait to replace the spark plugs until I replace the turbo. I knew the turbo was spewing oil because I’d see it in the intake manifold and throttle body (the valves look pretty good though...). However, when I was starting the car without the intercooler on I saw oil building up on the hose from the turbo and when using the accelerator it literally sprayed out on the engine! So I’ll wait to to put in new plugs until the turbo is replaced which hopefully won’t be too long.

    As for the misfire, the person I bought it from said there was low compression on #3 and no compression on #4. I didn’t test compression myself. It ran pretty terrible. I was hoping it was the head gasket and so I replaced that and a bunch of other things back in Dec., including using Engine Restore. After all of that work the engine ran a lot better. Granted, the improvement could mainly be because I replaced the spark plugs which were very fouled. But I still get #4 misfires. I have a compression tester but haven’t used it. The engine runs and it’s not too bad, but I know it could be better.
     
    jsilva, via an iPhone, Jun 18, 2020
    #65
  6. The_big_dill

    The_big_dill Greenie Member

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    I take it you didn't diagnose where the compression loss is coming from before you pulled apart the engine? Do a compression test before you get more work done.

    From what I have seen, Valves, rings and pistons are more common than head gaskets for compression loss on these engines.

    The bad turbo seals could be contributing to the smoke you experienced.
     
  7. jsilva

    jsilva Silver Member

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    I didn’t diagnose anything but simply hoped with the head gasket :) At the time even that was very ambitious for me. I’ve learned a lot working on this engine and so I have more confidence to do more serious work now.

    The main performance issues are that it’s pretty weak below 2000rpms and bucks somewhat when warming up, and the engine sounds a little grouchy all of the time. It also takes a couple of attempts to start when cold (it’ll start up and then stall). But once it’s warmed up, as long as I keep the rpms at 2700 or higher then it performs pretty well.

    There’s no visible smoke anymore.
     
    jsilva, via an iPhone, Jun 19, 2020
    #67
  8. The_big_dill

    The_big_dill Greenie Member

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    1. Compression test - this will define what you do next.
    2. Use a logger such as an accessport or diag tool to watch your fuel system pressure. There are a lot of weak points here. I am not going to get into the details, but do some reading on the pressure relief valve and how to test fuel pressure.
    3. Fresh plugs - don't forget to set the appropriate gap or the car will not run well at load.

    You may have a vacuum leak when cold.
     
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