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My 2007 6.0L K3500 Dually has a misfire P300

PAE

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Misfire PO300 or P300

No indication of cylinder or cause, cheap code reader not a $5K snackon scantool.

Uses alot of fuel is the only issue probably lacking power I just haven't noticed.

According to my figures mileage is 7.8 miles to gallon unloaded.

Next step ?
 
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M92PV4U

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Ls swa.... never mind. Random missfire I was corrected. Did you check the connectors on the injectors and coil packs? That is the easiest thing to do since you don't have a scan tool.
 
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gmcxt

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To accurately diagnose a computer controlled system you need a computer to access the data. You need a friend with a good scanner that can look up the misfire data PIDs. It will tell you which one(s) are misfiring and what fuel trims are.
 

xr-nut

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Ls swa.... never mind.
It's the number 3 cylinder did you check spark? Connectors on the injector and coil pack?

No it is not the #3 cylinder, or at least that is not what a P0300 code is. It is a "random misfire" code. see what gmcxt posted above and continue on.
 

SLOWPOKE693

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If everything is good in the ignition system a cam sensor relearn is what usually fixes that code. I've done it to at least 10-12 GM trucks over the years with good results.

Edit: might be the crank sensor relearn..... I've been out of the car business for five years and my memory isn't what it used to be.
 

M92PV4U

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To accurately diagnose a computer controlled system you need a computer to access the data. You need a friend with a good scanner that can look up the misfire data PIDs. It will tell you which one(s) are misfiring and what fuel trims are.

Is this tool capable of doing that? Encore Professional Diagnostic Tool.
 

xr-nut

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Is this tool capable of doing that? Encore Professional Diagnostic Tool.

Is that the OTC scan tool? If so, it has live date pids and will show you which hole(s) is misfiring. The last one here was a broken spark plug. Drove this truck around on a dozen test drives, no cel or any other issues. Sell it and the next day bam.....CEL. P0300 code, Snappy scanner showed the hole and found it. Somehow the end of the plug broke off.
 

M92PV4U

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Is that the OTC scan tool? If so, it has live date pids and will show you which hole(s) is misfiring. The last one here was a broken spark plug. Drove this truck around on a dozen test drives, no cel or any other issues. Sell it and the next day bam.....CEL. P0300 code, Snappy scanner showed the hole and found it. Somehow the end of the plug broke off.

Yes it is.
 

PAE

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Coils have been replaced, wiring / connectors good to coil packs.

Truck also sat for 6 months or so before and during the fire.



Op you are about three hours away from me but it looks like I have the correct scanner.
 
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M92PV4U

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Coils have been replaced, wiring / connectors good to coil packs.

Truck also sat for 6 months or so before and during the fire.

.

Screenshot_20200522-153117_Chrome.jpg
 

PAE

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I will be headed to LA in the next few months but I dont trust this truck enough to take it down there.
 

PAE

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One of the possibilities I've read about if all the other possibles dont pan out is a flat cam.

If its that this engine is toast. And will require replacement.

Im too old to swap out an engjne.

But I would supply the beer if anyone wanted to assist.
 

M92PV4U

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My 5.3 had a similar problem ifrc and it had a bent valve. It might be a good idea to change the spark plugs and do a compression test.
 

PAE

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Was one of the things I did along with plug wires and coils.

Have yet to do a compression check, will do that asap, and a leakdown test.
 

Truckedup

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If everything is good in the ignition system a cam sensor relearn is what usually fixes that code. I've done it to at least 10-12 GM trucks over the years with good results.

Edit: might be the crank sensor relearn..... I've been out of the car business for five years and my memory isn't what it used to be.

Yup, I dicked around trying to find the cause. An independent shop with a good rep couldn't fix it. Finally took it to a local Chevy dealer. , a relearn ,125 bucks, no problems after that
 

SLOWPOKE693

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Pay up and have sombody do the sensor relearn procedure!!!!

I'm betting it's the only thing that fixes it. Rest of the shit your doing is a waste of time and money. Dont be a cheap ass
 

ConwayMuddy

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You said it sat for a while, how much fresh gas have you had through it? I've had misfire codes with fresh, but shit quality fuel.
 

PAE

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Plenty I've been driving it since a month or so after the fire.

It also had a total dead electrical issue where it wouldnt crank that turned out to be a relay and a bit after that it had a ground problem and a new ground had to be fabricated for the coils.

This may be my subconscious mind why I'm making my old square body run again after 20 years.

Putting a sm465 into it, originally it had a T400.

I have been having a premonition about all electronic stuff in cars and trucks not working, and you cant push start an automatic transmission car or truck.

Im sure there are many stories online about emp and trucks etc not working after such a event.

As soon as I get the coin I plan to checkout the relearn process on the 07.

You said it sat for a while, how much fresh gas have you had through it? I've had misfire codes with fresh, but shit quality fuel.
 

Truckedup

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Plenty I've been driving it since a month or so after the fire.

It also had a total dead electrical issue where it wouldnt crank that turned out to be a relay and a bit after that it had a ground problem and a new ground had to be fabricated for the coils.

This may be my subconscious mind why I'm making my old square body run again after 20 years.

Putting a sm465 into it, originally it had a T400.

I have been having a premonition about all electronic stuff in cars and trucks not working, and you cant push start an automatic transmission car or truck.

Im sure there are many stories online about emp and trucks etc not working after such a event.

As soon as I get the coin I plan to checkout the relearn process on the 07.

You can push start an auto tranny if it has a pump on the output like some of the 50's stuff....lol
 

BIG-O

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The P0300 random misfire code on my 03 6.0 ended up being #1&7 spark plugs. Found that one out the hard way after doing intake gaskets then taking it to the shop.
 
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Crack head chipmunk got into your wire harness under the fuse box, perfect hole in the back of the box for it to get in, Fucker ate my fuel pump wire, no start.
 

PAE

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No and now it also has a PO335 or PO355 crank position sensor that is giving an intermittent code.


Taking it to the Chevy stealership soon.

FML


@OP

Did ya fix it yet???
 
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