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My strange misfire situation

Discussion in 'Coyote Series Engines' started by PWslow5.0, Feb 19, 2017.

  1. PWslow5.0

    PWslow5.0 New Member

    Jan 28, 2017
    I've been getting very, very weird misfires, I'll just get right to it.

    Bought bone stock 2012 GT 55k miles on 2/2015 . Been doing small stuff here and there. Had a misfire in 3 and 5 and a p0300, replaced the coils ran good. I had the same p0300, p0303 and p0305, so I changed the coils and the car ran great again.

    12/2016 66k miles
    Mods are Cobra jet, vmp 67mm, jlt intake, long tubes.

    Codes and situations.
    Codes have only been p0300 p0303 p0305, never any other code or cylinders.

    Most of you know the styles of CEL.

    The flashing CEL has happened 4 times. The situation is after a pull, in 5th gear letting the engine rev down at roughly 5000-6000 rpm and slowing down. The CEL would flash, protecting the cats (deleted), with no power until the light went away. Then my car was back running back to 95% like nothing happened. The codes every time would be random misfire p0300 and misfire in cylinder 3 and 5. The CEL does not stay on but was stored.

    This misfire is ONLY at wide open throttle and 95% of the time it DOES happen, it misfires with no CEL. In fact datalogs show fuel, spark, timing, everything is on point.
    I can be in 2nd, 3rd, 4th, 5th and hammer down. The misfires are very fast. .1 seconds, in each gear I can misfire any where from 0 to 10 times extremely fast. They're too fast to count, the engine loses power for that split second, time adds up. I don't want to damage my motor. It pulls really strong. Those misfires are quick, but something is not right.

    Changed coils, plugs again. I moved injectors around. Compression test, leak down test, fuel pressure test, fuel volume test. I've checked for leaks at the manifold, head, throttle body, air intake, air filter, pcv.
    I've got the monoblade and another tune and STILL had wide open throttle misfires.

    I'll attempt to upload a video file after this so you can hear the misfires from inside my car. Because the sound is indescribable at how quick it is.

    Any help or advice is is appreciated.
  2. Waco5.0

    Waco5.0 New Member

    Sep 4, 2018
    Ever figure this out?

    Sent from my SM-G950U using the svtperformance.com mobile app
  3. 93TealSK

    93TealSK New Member Established Member

    Sep 5, 2007
    Southeastern PA

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