454 Vortec P0300 Multiple cylinder misfire code. Troubleshooting and solution.

Discussion in 'Engine Performance + Maintenance' started by Mangonesailor, Aug 18, 2015.

  1. Mangonesailor

    Mangonesailor I'm Awesome

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    Ttoyota, you had the distributor checked out? What about the ignition module?

    The dizzy is a Billet summit unit, but the cap and rotor are MSD. I felt little difference between the two. The shafts should all be the same (steel). The difference is the dizzy body, as the factory one is made out of plastic. (It's made of plastic, not aluminum. Was talking to multiple people at work)
     
    Last edited: Jun 8, 2018
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  2. Ttoyota

    Ttoyota OBS Enthusiast

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    No the alternator. I pads aren't the best for this. Sorry.
     
  3. Ttoyota

    Ttoyota OBS Enthusiast

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    I'll order new cap and rotor and try and cam position sensor once I get back from work. I tried ignition module and it didn't change. No telling. Motor has 180k on it so it could be timing chain valves compression who knows? The night have to do everything you did plus more. Or it could be this 411 with this base tune. Hard to say. I will vouch for iridium plugs though I put these conventional cheapies in and alt hoo
     
  4. Ttoyota

    Ttoyota OBS Enthusiast

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    I did try a new cntrl module it didn't help either. Could it be possible that the tune that the 411 was set up with is off? I will be outta pocket for a while so I won't be able to do any troubleshooting. Got a remote operated vehicle out in rig to tinker with. Yippie
     
  5. Christian Steffen

    Christian Steffen I'm Awesome

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    Pretty unlikely it is the tune, unless it is always running pretty lean, which the o2 sensors should prevent.
     
  6. Mangonesailor

    Mangonesailor I'm Awesome

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    Yeah, I doubt it's the tune. Like I said, need some more data. Otherwise id be shotgunning ideas.

    So, you've got good fuel pressure? No spark leakage from the wires ? It's possible the chain is old and worn. You can check via the crank timing marks. Turn the crank until at the end of the span of carnal points on the crank. Then turn the motor backwards until the rotor moves. The difference in degrees is your slop. I want to say 7° was supposed to be too much and 5° was acceptable.

    Could be a clogged cat? Does it run hot?

    How does it run at speed, like 2500rpm? Can you hear it miss at idle and revved up?

    Have you checked for clogged/leaking fuel injectors?

    And you should probably do a compression check I suppose.
     
  7. Ttoyota

    Ttoyota OBS Enthusiast

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    I will definitely update.
     
  8. Ttoyota

    Ttoyota OBS Enthusiast

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    New injectors. Brand new wires. Ill have to check fuel pressure and slack can't do much till im back home. Running pretty good though so i might do what i can when I can.thanks for all the input though.
     
  9. Mangonesailor

    Mangonesailor I'm Awesome

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    I googled around some more. 10* slop is too much and 5* is expected/acceptable.
     
  10. Ttoyota

    Ttoyota OBS Enthusiast

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    Thanks sailor ill check it first thing when i get home.
     

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