F-150 Problem

Discussion in 'Technical & Modification Discussion' started by v8p71, Oct 7, 2009.

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  1. Oct 7, 2009 #1

    v8p71

    v8p71

    v8p71

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    aight so my brother owns a 99 F-150 with the 4.2 v-6. has about 160,000 miles on it.

    we had to replace the engine at 100,000 (metal shavings in the oil FTW:thumbsup:)

    so we got an engine with 50,000 miles and had a shop swap the two.

    after a year or two, the engine started misfiring. so we changed the plugs, and the wires, which fixed the problem for about a month. when it developed the misfire again, we took it to a shop, where they said they didnt see anything.

    it misfires in 4th and 5th gear when you try to accelerate. y'all got any ideas?

    my brother loves his truck, but i seriously think he needs to find a new one.
     
  2. Oct 7, 2009 #2

    BrandonKupihea

    BrandonKupihea

    BrandonKupihea

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    I am wondering if it could possibly be the injectors?
     
  3. Oct 7, 2009 #3

    iminhell

    iminhell

    iminhell

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    Well really if you can't narrow down when it started happening, after a year or two is pretty damn vague, you'll not know if anything else was neglected or replaced at/around the time to narrow what could be causing the problem.


    But being it seems to be related to load I'd have to guess injectors, fuel pump (all filters included), plug gap/style/heat range, ignition resistance, alternator (the voltage is computer controlled and used in part to figure load), on and on.

    Best bet is to scan it for pending codes or freeze frame data and go from there.