New engine, old issues still haunting after rebuild

Discussion in 'Mazdaspeed 3 Troubleshooting' started by mituc, Sep 15, 2019.

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  1. mituc

    mituc Greenie Member

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    So back in June I had a catastrophic engine failure caused by some work we did on the factory intake manifold: VTCS removed and slightly ported, and the holes between the runners were sealed with some studs and then the fabricator used some melted tin to hold them in place. No, it was not a good idea. These ones were retrieved while still attached on the intake manifold, almost came off by hand:
    [​IMG]
    One just as big as the first one which was sealing the hole between runners on cyl #2 and #3 came off and this is what still stayed in one piece after somehow getting past the intake valve without even touching it and then being shattered by the piston and one of the intake valves:
    [​IMG][​IMG]

    The spark plug on that cylinder looks like this (I still have it, I will send it to the ZoomZoomBoom Museum when we will have one):
    [​IMG][​IMG]

    The piston wasn't happy, and neither was the head:
    [​IMG] [​IMG] [​IMG] [​IMG]

    [​IMG] [​IMG] [​IMG] [​IMG]

    [​IMG] [​IMG] [​IMG]

    [​IMG] [​IMG] [​IMG]

    Fast forward to these days... the engine was rebuilt (used the spare block I was keeping under the bed) with 88mm pistons, CorkSport cams fitted on a spare head, a new shiny GTX3071R gen2 which replaced the gen1 I had. I also replaced the injectors as I had a spare set which I've sent for ultrasounds cleaning and measurements, used the new CorkSport injector seals which I had as a spare, and so on. Apart from this the rest of the setup is the same (manifolds, exhaust, and so on) because my ambition is to up the power and acceleration record for full emissions complaint 2.3DISI-Ts (my car did 3.62s for 60-100mph and 476whp on the old setup).

    When I exited the car shop right after the rebuild everything looked fine, but I wasn't pushing the car as I still was on 10w30 break-in oil. On the way home (250miles/400kms drive) I started to push the car a bit and I noticed it starts cutting and stuttering at the boost level where meth kicks in (meth comes on at 14PSI, I noticed break-ups at 12-14-16PSI of boost).
    I thought is something meth related so I flashed a pump-gas only map, but the problem is the same.

    During the stuttering I kind of hear the mixture burning into the exhaust, so I figured I may have some ignition issue. I measured the ignition coils and indeed one of them was at 430Ohm, the rest of them were at 1.65-1.72kOhm. I quickly swapped that coil from my CX7 and I thought I fixed the problem, but not really even though something got better. And of course it did, today I wanted to use the CX7 and after 2 minutes it lit the check engine light, misfire cyl #1.
    This is how it sounds like when I push the gas a little firmer:


    At this point I have no idea how to go further. And I want this car fixed badly. I started looking for a spare ECU in case the short on that destroyed spark plug got even further past the ignition coil.

    The logs look relatively clean, the car is down on power but that's pretty much it. I see no knock or anything weird. The AFRs go down to 10 or even below (9.9, 9.8) while I'm targeting 12 and that the only thing I can see in the logs.
    Once I pushed it while it was stuttering and I got a misfire on cyl #2. Never came back after clearing it but now I'm thinking if maybe I have a problem with that injector.

    So what do you guys think?
     
  2. Eroler1

    Eroler1 Greenie Member

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    hows the coilpack harness? mine was misfiring since i mess up the wire tuck but sometimes when taking out engine these harness loves to get wedge and stretched on somewhere they arent supposed too.
     
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  3. andale927

    andale927 Silver Member

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    Also even though you are having the issue on only 1 of the coil packs it wouldn't hurt to make sure the coilpack harness ground wire is okay.
     
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  4. mituc

    mituc Greenie Member

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    Do you happen to know where that goes? On that big metal bracket under the intake?
    I just noticed my back-up lamp works intermittently, maybe it's something stupid wherever all these attach. The gearbox sensor should be ok as it was just fine prior to rebuilding the engine.

    Mine looks ok, but who knows. I inspected it from the coil packs back to that big connector near the fuel pump.
     
  5. mituc

    mituc Greenie Member

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    Ok, I remember cleaning that one... it's right there on the valve cover.
     
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  6. JohnnyTightlips

    JohnnyTightlips Platinum Member

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    Did you check the fuel pressure relief valve? When mine was going out as soon as I tried to get into WOT it would cut out and go no where. It could be requesting fuel and there is not enough there. It doesn't sound like that is your problem but it is something to check.

     
  7. mituc

    mituc Greenie Member

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    I thought about that too... but it's too much of a coincidence for the problems to start right after the rebuild, and also if the PRV fails you'd see the fuel rail pressure going very low. In my case FRP is good... Basically that's the thing, everything looks good, I get no errors that I can use to figure out the issue, I get no real clues in the logs apart from the AFRs going rich.

    I blocked the EGR a few days ago, apart from the fuel consumption increase there's no other thing happening. I will unblock it when I will get the chance because the EGR doesn't seem to be leaking now I suspected.
     
  8. mituc

    mituc Greenie Member

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    Ok, so this was caused by cracked spark plugs which I opened a different thread for.
     
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  9. JohnnyTightlips

    JohnnyTightlips Platinum Member

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    Really glad you figured it out. I wonder how they got so bad.
     
    JohnnyTightlips, via a mobile device, Nov 7, 2019 at 8:20 PM
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