GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 5 of 5
  1. #1

    Default P0300 Rough Idle ideas? 2004 Z71 5.3

    Ok as I posted last week I bought a 216k Mile 2004 5.3L Z71.

    I knew the cig lighter dident work (dident really care) but the truck was idleing slightly rough this I also knew, but their was no CEL. Running it today a CEL came on, put my basic reader on and no power, goggled and found that a blown cig fuse can cause no power to the reader connection and it worked, ran it and got a p0300.

    Now the previous original owner "thinks" he had half or all the plugs changed at about 150k when he had a cracked head replaced but not sure. I have that "need a tune up smell" from the exhaust not completely rich smelling just that incomplete combustion smell. Air filter is clean, I just cleaned MAF nothing.

    So my first step is plugs I ordered NGK IZTR5B11 Laser Iridium That are pre gapped .40. Should I use these? Return and get AC Delco Platinum? Iridium? Should I go with wires or see if plugs?

    Other things I have read clean the flapper on the TB (wifes Mazda 3 would run rough after pulling battery due to carbon build up) and pull and clean or replace IAC Valve.

    Any other quick cheap fixes before I get too deep into digging?

    - - - Updated - - -

    Scratch that put the NGKs In and AC Delco 9748HH wires I got from Advanced Auto and all is well running great under throttle and idle is butter smooth.

    Stock plugs were the worst I have ever seen! They look every bit of 216k miles.........

    - - - Updated - - -

    ALSO cleaned TB while I was their

  2. #2

    Default

    ....

    2009 Chevrolet Silverado 1500 LT Z71 Crew Cab "All-Star Edition"

    Line-X'd Bed
    Line-X'd Custom Brush Guard(Heavy Duty)
    5.3L Flex Fuel
    Factory Black Running Boards
    BF Goodrich All-Terrain KO's(265/65R18)
    2" Rough Country Leveling Kit
    EGR In-Channel Vent Visors
    Exterior PLUS Package
    Interior PLUS Package
    K&N Drop-In Air Filter
    Bowtie Mud Flaps
    Cat-Back Dual Exhaust
    Black Bowties
    DeeZee Toolbox(Debadged)
    Diablo Sport Predator(AFM Disabled)
    ProFlaps
    Towing Mirrors
    Next Planned Mods
    Bigger Tires
    Aftermarket Rims

  3. #3

    Default

    you can do the whole seafoam thing and see if that helps any.

    Have you changed the fuel filter yet?
    2000 Silverado 5.3L Z71 4x4: K&N air filter, Procomp 16x8 rims, 285/70R16 Toyo AT2s, Kenwood head unit, Alpine 500.1 amp, 12" kicker, Infinity 5.25" speakers, Bilstein HD shocks, EBC GD Sport dimple & slotted front rotors w. EBC green stuff pads, Brembo slotted rear rotors & HIDs.

  4. #4

    Default

    Quote Originally Posted by afireinside View Post
    Ok as I posted last week I bought a 216k Mile 2004 5.3L Z71.

    I knew the cig lighter dident work (dident really care) but the truck was idleing slightly rough this I also knew, but their was no CEL. Running it today a CEL came on, put my basic reader on and no power, goggled and found that a blown cig fuse can cause no power to the reader connection and it worked, ran it and got a p0300.

    Now the previous original owner "thinks" he had half or all the plugs changed at about 150k when he had a cracked head replaced but not sure. I have that "need a tune up smell" from the exhaust not completely rich smelling just that incomplete combustion smell. Air filter is clean, I just cleaned MAF nothing.

    So my first step is plugs I ordered NGK IZTR5B11 Laser Iridium That are pre gapped .40. Should I use these? Return and get AC Delco Platinum? Iridium? Should I go with wires or see if plugs?

    Other things I have read clean the flapper on the TB (wifes Mazda 3 would run rough after pulling battery due to carbon build up) and pull and clean or replace IAC Valve.

    Any other quick cheap fixes before I get too deep into digging?

    - - - Updated - - -

    Scratch that put the NGKs In and AC Delco 9748HH wires I got from Advanced Auto and all is well running great under throttle and idle is butter smooth.

    Stock plugs were the worst I have ever seen! They look every bit of 216k miles.........

    - - - Updated - - -

    ALSO cleaned TB while I was their
    I am amazed that spark plugs can actually go 200K+ miles. I would have bought the same brand and installed those. You might want to run a can of fuel injector cleaner in the gas tank.

    IMO, the steps you do when buying a used vehicle:

    Change rotor and distributor cap(if equipped).
    Change plugs, and if the vehicle has high mileage, change the wires.
    Change oil and filter.
    Lube job(if you can).
    Change transmission fluid.
    Change differential and transfer case fluid if equipped.
    Coolant system flush.
    Change air filter(K&N).
    Change serpentine belt.
    Change brake fluid.
    Change fuel filter.
    Run a bottle of fuel injector cleaner in the fuel tank(gas engines).
    Get AC refrigerant levels checked.
    Change cabin air filter.
    Clean throttle body.
    Inspect tires for wear and have alignment checked.
    Change power steering fluid.
    Inspect rubber hoses for possible leaks.

    I know this seems like a lot, but unless I knew the previous owner and was sure they stayed on top of the required maintenance, I would feel better having these things done.

    2013 Silverado LTZ White Diamond Crew Cab


    Mods:
    Advent OGM1 Navigation
    Husky Liners GearBox Underseat Storage
    Airaid MIT
    EGR Rail Caps
    K&N Air Filter
    Flowsound 40 Muffler
    Hypertech Max Energy Tune (only top end limiter removed and AFM disabled)
    Chrome Tailgate Handle Cover
    TonnoPro HF-155 Tonneau Cover
    WeatherTech Front and Rear Splash Guards
    Husky Liners X-Act Contour Floor Liners
    WeatherTech Side Window Deflectors

  5. #5
    Legend

    Join Date
    Sep 2010
    Location
    everett, massachusetts
    Posts
    1,317

    Default

    I would use the ac delco irridium plugs. you do not adjust the gap. if you do you will damage the small tip. if the gap looks off the plug is defective !

    before replacing any plug wires measure the resistance. many new wires are defective with POOR quality control.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •