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New coyote gen 2 stock replacement not running right

Discussion in '5.0L Coyote V8 Engine Modification/Discussion' started by Dave Johnson, Jul 28, 2019.

  1. Dave Johnson

    Dave Johnson New Member

    Jul 27, 2019
    princeton, MN
    Hi I just finished installing a brand new coyote crate motor in my 2015 mustang after I bent valves in the original one. Brand new motor from Ford Performance through Summit racing and I'm getting an intermittent lean condition and random misfires, usually mid throttle, cruising with the revs up aroung 2-3k. I upshift into overdrive and it clears itself up after maybe 10 seconds but it seems to keep coming back. This is a brand new motor complete with injectors, intake, throttle body, almost everything. I still have the factory fuel pump, o2 sensors and computer. I did upgrade to the BBK headers and cat delete, and have the proper tune for those. Same difference on factory tune or new tune. Any of you guys have any ideas what could be doing this?

    Update: new O2 sensors upstream and no change. Still stuttering just a little while cruising and then the way lean condition and bad bogging for about a mile of driving.
    Last edited: Jul 28, 2019
  2. fuelforfire87

    fuelforfire87 Active Member Established Member

    May 7, 2015
    Lemont, IL
    Are you using o2 extensions on the front o2 sensors with the headers? If so get rid of them they are known to cause issues especially the BBK ones. You can disconnect the wiring harness at the top of the bellhousing of the transmission to get the extra slack for them to reach without the extensions. I used to have bbk headers on my 14 GT and i had a CEL until i ditched the o2 extensions.

    Sent from a Chevy S10+

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