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1999 Silverado 1500 5.3L with P0304 error

Discussion in 'Chevy Trucks' started by pablo43, Dec 9, 2009.

  1. pablo43

    pablo43 Junior Member
    Messages: 2

    I was just plowing with my 1999 Silverado and the check engine light came on. When I went back to the house I pulled a P0304 error (cylinder 4 misfire). I did not notice any running problems with the truck. Has anyone else had this error and what is the usual solution(s)?

    Any help would be appreciated.


  2. stacks04

    stacks04 Senior Member
    from ct
    Messages: 119

    maybe a drop of water in the fuel or piece of junk in the injector. if it is running fine than clear it and see if it ever comes back.
  3. whitextreme

    whitextreme Junior Member
    Messages: 10

    Check the fuel pressure regulator and clean the mass air sensor. I had the same problem with my truck and that was the problem. Pull the vacuum hose off of the regulator and if there if fuel in there it is bad.
  4. Thermos017

    Thermos017 Member
    Messages: 59

    when was the last time you checked your cap and rotor? i believe the 99 was included in the years with the flat cap that collected too much moisture (need to clean the vent in the bottom of the distributor when you change caps) and caused premature corrosion. if that's the case, be sure to replace the cap with the aluminum contact one, not the brass contacts.

    also, we had a misfire that was very random. never the same cylinder twice in a row. eventually it got to the point that it was causing a jerk while driving down the road (like you were randomly slamming on the brake for a split second). this went on over the course of about a month and a half. turned out the cat was falling appart and causing excess backpressure. we didn't ever see the full time loss of power, or the lack of power up hill that you usually get with a failing cat. just that jerk and the misfire code. welded in a new one and the truck ran like new again. we never did get an error code for catalyst efficiency on that one either... just the misfire codes about once a week at first, and right before we found the problem it was at least one code per drive cycle.
  5. ahoron

    ahoron Senior Member
    from here
    Messages: 422

    Time for plugs and wires.