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Help 94 f150 4.9L strait 6 misfire and black smoke

Discussion in 'Air Intake, Engine Electronics, Ignition & Exhaust' started by Ethan Thomas, Apr 7, 2017.

  1. Ethan Thomas

    Ethan Thomas New Member

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    Just randomly out of no were my 94 f150 just cut off one morning as I was warming the truck it started back immediately and has not died agin but the check engine light is on and truck is misfiring if I compress the gas pedal too hard it won't accelerate it just jerk if I let you press it I can slowly take off in the afternoon the truck drive better than the morning it still start every time with no hesitation I've changed every sensor I could think of that could cause black smoke and misfire and loss of power and don't know what to do here any help would be greatly appreciated thanks
  2. redrag

    redrag Active Member

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    look for fuel in the vac hose to the fuel rail pressure regulator. the diaphragm could be bad
  3. Dominick 1

    Dominick 1 Well-Known Member Respected Member

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    Welcome to the Forum
    Have you went to a place like AutoZone and have the codes pulled from your truck
    that would be a good place to start to find your issue
  4. Dominick 1

    Dominick 1 Well-Known Member Respected Member

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    Unplug your mass air sensor and see how it reacts
  5. Ethan Thomas

    Ethan Thomas New Member

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    I've replaced the FPR even though I did not see fuel in the vacuum line I've also replaced the maf sensor along with lots of others.. can it be the computer or valve stem seals
  6. Ethan Thomas

    Ethan Thomas New Member

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    They say they can't test it because it's an obd1 but I've tried testing it myself but just got codes for sensors and a faulty ecm but those codes may not have been read correctly
  7. Dominick 1

    Dominick 1 Well-Known Member Respected Member

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    http://straighttalkautomotive.com/OBD1/ford-OBD-I.html
  8. Skyhawk

    Skyhawk Active Member Respected Member

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    Try to find this book regarding OBD I Ford products. "How to Understand, Service and Modify Ford Fuel Injection & Electronic Engine Control" By Charles O. Probst, SAE. Published by Robert Bentley Publishers. The years covered in my addition are 1988 to 1993, but there may be a later addition. If there is not a later addition I would bet there is little if any difference for the 1994 model year.
    Next, black smoke generally indicates a rich fuel mixture condition. Some possibilities for the cause are; Injector (s) sticking open, O-2 sensors failed and the computer will automatically go to a rich mixture condition so you do not burn a valve or piston, Running on a rich mixture for a time period will cause the catalytic converters get clogged and this will cause a lack of power, stalling, and other drivability issues with the engine. A good muffler shop can tell you if your exhaust system is clogged. Also note that there is a relatively unsophisticated way to pull codes from an OBDI system. Check on the SHO forum and look at your model year for the process of pulling the diagnostic codes or check Dominic's recommended site.

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