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No Start Situation, need your help

Discussion in '80-Series Tech' started by maddss, Feb 9, 2017.

  1. maddss

    maddss

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    94 LC, Over the pass few months I have been chasing a engine stumbling issue while driving. No codes to help that issue. Yesterday the LC ran with no problems. Today my LC will not stay running, It starts then dies immediately. Pulled the following codes: 21, 42, 32 and 71(I always get this one).

    Code 21 Main oxygen sensor signal fault
    Code 32 Air flow meter circuit or Vacuum sensor signal fault
    Code 42 Vehicle speed sensor circuit
    Code 71 EGR system malfunction


    I have already replaced the Plugs, Wires, Cap and Rotor. Items to be replaced Fuel Filter and Filter Sock.

    Any help or suggestions would be greatly appreciated.
     
  2. jonheld

    jonheld

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    That screams AFM to me. The fuel pump is run from both the starter circuit and AFM circuit. IOW, the fuel pump will run while the starter is cranking. When the engine starts sucking air, the flap in the AFM opens and fires the second circuit that keeps the fuel pump running.
    When you stop cranking the starter, if the AFM flap or associated wiring is faulty, the fuel pump won't continue to run and the motor will stall.
     
  3. maddss

    maddss

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    @jonheld Thanks

    Just cleared the code. Also check the connections under the black cap and one of them is loose.

    Now looking for a rebuilt VAF or someone who can rebuild it.
     
  4. jonheld

    jonheld

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    There is a diagnostic in the FSM.
     
  5. maddss

    maddss

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    Back in the summer I made the bad bad mistake and unscrewed the Phillips screws and broke the welds. Its been soldered and its not holding, I was able to wiggle the terminals and the truck runs.