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Engine misfire

Discussion in '2nd Gen - 2003 - 2006' started by Andy Gar, Jun 23, 2020.

  1. Andy Gar

    Andy Gar New Member

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    My 03 Expedition 5.4 With 189K started misfiring a few months ago, it was running rough, the Service Engine light would flash and a ton of codes came on at once including 301 and 307 so I figured plugs and coils. I replaced all plugs and coils with Motorcraft brand and it ran great for a couple of months. Last month it did it again, same codes, same cylinders misfire, so after asking a tech a the Ford dealer I replaced the ECU. So now with the new ECU I only get 3 codes 300, 301 and 307... but it is still misfiring and not running at full power. I replaced the coil and injector pigtails for cylinder 1 because the plastic tabs were broken, but still no change. What next, should I change fuel injectors?
     
  2. riphip

    riphip Full Access Members

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    Also check your vacuum lines. PCV area, behind batteries, etc. They get old & cause a lot of ignition/running problems.
     
  3. Hamfisted

    Hamfisted Full Access Members

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    What did you do to cylinder #7 ? You said you had a P0301 & P0307 . You worked on cylinder #1 , but what did you do to cylinder #7 to fix it's miss ?





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