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some times a rough idle and back firing

Discussion in 'Ford Trucks' started by Fannin76, Oct 12, 2014.

  1. Fannin76

    Fannin76 Senior Member
    Messages: 731

    As the title says some times my 97 f150 with a 4.6 liter will idle rough or back fire when getting into it. Also some times it'll shake while accelerating or just feel like its completely lacking power. Any thoughts?
     
  2. kimber750

    kimber750 PlowSite Veteran
    Messages: 3,665

    Start with code reader. Most auto part shops will scan for free.
     
  3. Fannin76

    Fannin76 Senior Member
    Messages: 731

    No check engine lights are on though
     
  4. kimber750

    kimber750 PlowSite Veteran
    Messages: 3,665

    I would still have it checked. Just so many things it could be. MAF, fuel pump dying, bad O2, bad cat and so on. You can test fuel pressure, unplug MAF and see if it runs any different. Bang on cats. But in the end I would bet on MAF but that should throw a code.
     
  5. Fannin76

    Fannin76 Senior Member
    Messages: 731

    It feels like its clogged up like a bad cat. Feels like I need to rev it up and blow it out
     
  6. Fannin76

    Fannin76 Senior Member
    Messages: 731

    OK so had it read.......oh boy 36 codes. Basically needs a full tune up. Plugs,wires,rotor button and cap, dpfe sensor,02 sensor bank 1 sensor 2, 02 sensor bank 2 sensor 2, cylinder 2 misfire,cylinder 7 misfire,Fuel system to lean.....holy crap
     
  7. kimber750

    kimber750 PlowSite Veteran
    Messages: 3,665

    Test fuel pressure, weak pump can cause a lot of those codes.
     
  8. Fannin76

    Fannin76 Senior Member
    Messages: 731

    How do you do that? And what should it be?
     
  9. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,972

    Don't worry about the o2 codes just yet. That might be b/c the misfire
     
  10. Fannin76

    Fannin76 Senior Member
    Messages: 731

    Would it misfire because low or high fuel pressure
     
  11. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    Low

    Autozone has a rental kit.

    Should probably be around 50 but I'd have to look it up
     
  12. kimber750

    kimber750 PlowSite Veteran
    Messages: 3,665

    Low fuel pressure can cause your lean condition which will set off misfire and O2 codes.
     
  13. Fannin76

    Fannin76 Senior Member
    Messages: 731

    so of its low is that a bad pump?
     
  14. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,972

    Usually yes but could be regular, or rarely a filter
     
  15. Fannin76

    Fannin76 Senior Member
    Messages: 731

    I changed the filter already....the regulator has the vac line with diaphragm inside?
     
  16. kimber750

    kimber750 PlowSite Veteran
    Messages: 3,665

    Bad pump, bad regulator or clogged filter. You can try pulling vacuum line of regulator, that should bump the pressure. With out fuel pressure tester it is hard to say what exactly. Still could be something else. I am leaning towards fuel pump but I could be wrong.
     
  17. kimber750

    kimber750 PlowSite Veteran
    Messages: 3,665

    Seems I am a slow typist. :laughing:
     
  18. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,972

    Ah, I'll give you that. After surgery and all
     
  19. Fannin76

    Fannin76 Senior Member
    Messages: 731

    So would this also explain the truck dying when back my trailer down the drive and manuvering it it around the conner and into position?
     
  20. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    Dude go to aurozone and get a free guage set. Anything else is just guessing and throwing parts at it