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Thread: Idle misfire Nš4 and no power after 0 PSI boost

  1. #1
    Guest suixo's Avatar
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    Idle misfire Nš4 and no power after 0 PSI boost

    Got an S14 SR in my S13, so I thought I'd post here.

    Friday I floored it and blew the hose from the turbo to the EBC solenoid. The overboost blew the valve cover gasket, melted spark plug Nš4 and I think caused a small leak right after the turbo at the intake elbow (before IC).
    Now I got a horrible idle, cause by Nš4, and absolutely no power after 0 PSI of boost (works perfectly in between, can sometimes get 6 PSI).

    I fixed the valve cover gasket and changed the plugs, changed the intake turbo elbow gasket, removed and checked every air hose, swapped coil packs, swapped TPS, moved wires around, checked coils packs wires, checked Nš4 Injector...
    It all seems fine.

    The worst part is that everytime I change something like the packs or the TPS yesterday, the idle problem gets fixed, then starts to fail again after 1 hour or next day. (Misfire after 0PSI was never fixed though).

    Conditions:
    - Idle Boost: -20
    - Decel Boost: -23
    - WOT Boost: up to 2-3 PSI then completely misfires on all cyls

    - Idle AFR: 14.5-15.5 When not misfiring, misfires appear random and are definitely Nš4 since unplugging the coil pack makes no change (all others do). AFR jumps to ~16.5 when a misfire happens.
    - Cruise AFR: 14.5-15.5 After 2000RPM almost exactly everytime the misfire disappears and the car runs fine (until i get in boost where it fails again).

    - Compression checks ok (140PSI)


    I still have stuff to check, probably dismantle the entire intake side today and check all sensors, but I think it could be a sensor or wiring problem (worth noting i made the harness myself and is 6 month old). I was wondering if those symptoms have happened to anyone before and what could the cause be. Maybe I can save a lot of headaches.
    Thanks in advance for any help or ideas!

  2. #2
    Guest finnnerz's Avatar
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    Have you checked that it hasn't got a boost leak anywhere?

    Sent from my ONEPLUS A5000 using Tapatalk

  3. #3
    Guest suixo's Avatar
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    Short of taking the intake off...yes. I was going to do that today but opted for getting the nissan scandata program and connect it to the computer with the consult. I made a few runs with logs and i'm reviewing them right now.

    What i learned so far is error code for MAF, Knock and ignition. And the timing is all over the place. When the TPS goes up quick, the timing goes down fast until is catches up. It's bogging for some reason. Weird thing is that the MAF line and the TPS line matches perfectly, and the MAF line is steady, smooth.

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