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

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Mangonesailor

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

How did your truck run after the MSD cap?
I've just got stock AC Delco on mine, but I'm probably going to have the whole distributor replaced with a billet shaft when I do my 0411 because I've noticed two other members who have had issues with the distributor shafts after swapping computers.

I was gonna go back to Delco but I'm curious if you noticed any difference in performance.

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)
 
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Ttoyota

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

Ttoyota

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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
 

Ttoyota

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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
 

Christian Steffen

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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

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

Mangonesailor

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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.
 

Ttoyota

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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.
 
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