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 P0300 troubleshooting 
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Post P0300 troubleshooting
It's a 2006 Yukon 5.3

Im getting a blinking P0300. Minutes after it starts.If I erase the code when it warms up sometimes it doesn't come back .While driving it would show up again. If I shut down I'll get a solid a check engine light with P0300 sometimes P03001.

The idle is not smooth.

I changed plug no. 1 and the insulator is cracked.I don't know if I broke it while taking it out..Same idle and symptoms.

I switched coil 1 and 2 - no change

I'm going to change the rest of the plugs when find time but before I do I want to pull out injector 1 check

Any tips on what to do first..?


Thu May 12, 2016 6:25 pm
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Post Re: P0300 troubleshooting
Could be intake gaskets sucking air when cold and they seal up when it warms up. Very common on those motors. Just swap the injector to another cyl and see if the code follows it.

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Thu May 12, 2016 8:28 pm
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Post Re: P0300 troubleshooting
Clogged cat?

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Fri May 13, 2016 11:07 am
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Post Re: P0300 troubleshooting
Ill swap the injectors, change the plugs and check for a vac leak.

Thanks


Fri May 13, 2016 1:10 pm
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Post Re: P0300 troubleshooting
6speedIROC wrote:
Clogged cat?

Usually you end up with misfires on 1,3,5,7 or 2,4,6,8 depending on which one is plugged

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Fri May 13, 2016 6:56 pm
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Post Re: P0300 troubleshooting
Didn't have time to change the plugs but I got to swap injector 1 and 3


Still doing the P03000 but after driving it around the block with the flashing p03000 I shut it down and restarted. Gave me a flashing a P0300 again.Shut down and read.

This time P0303..Never got this before so I assume it's the injector that I swapped over fROM cylinder 1

The LT trim is at 12.98% on bank 1 which Google said is high compared to bank 2 at 7%..

I'll change the injector suspected bad injector and the plugs

Makes sense? If that doesn't work what's next?

Thanks flame


Sat May 14, 2016 7:42 pm
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Post Re: P0300 troubleshooting
Replacedthe injector.. no more P00303. But still getting P0300 and rough idle. I replaced 7 of 8 spark plugs ran out of time with plug 8. The idle got a bit better but still code comes flashing .It doesn't stay lit and sometimes disappear. Smells like rotten egg in the exhaust.

O2 and evap system never gets ready. One of the o2 readings doesn't give a percentage just --%

Any ideas..I'm thinking either 02 sensor or injectors


Tue May 17, 2016 8:09 pm
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Post Re: P0300 troubleshooting
Anybody have a set of coil packs and/or injectors they want to sell?


Thu May 19, 2016 8:38 am
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Post Re: P0300 troubleshooting
How is the 5.3 for carbon build up? I've dealt with cars before where the only thing that got rid of the random misfire was a thorough throttle body cleaning.

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Sun May 22, 2016 12:41 pm
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Post Re: P0300 troubleshooting
Can you get misfirr data? The counts per cylinder will tell you more than the codes. In the 17 years these motor have been out I've only replaced 2 coils.

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Sun May 22, 2016 7:38 pm
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Post Re: P0300 troubleshooting
Drove it with the P0300..It finally progressed to a P0303. Its the same coil that I took from Cylinder 1. Replaced the coil and no codes so far, and its running smooth..so far.

I just have to fix the A/C and Im done. Is the A/C system on these motors the same as thirdgen/4th gens?

Thanks for the help


Tue May 24, 2016 7:58 am
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Post Re: P0300 troubleshooting
Try cleaning the MAF sensor and throttle body also and see if it will solve the problem.


Fri Dec 14, 2018 1:31 am
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