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2014 Silverado 5.3 P0300?

jrob56

By jrob56
in Troubleshooting & Recalls

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jrob56 Enthusiast

jrob56

Posted
Posted

Hey guys,

 

Yesterday running some errands, I was down on power and CEL started flashing. Killed the truck started back up and ran perfect, happened one more time and I swung by autozone because I was close. P0300 showed as pending, not set yet though.

 

I have been running E85 mostly lately, tank of 87 here and there. Had a full tank of E85 in it at the time. I have occasionally had some hard starts, 3-5 second crank before start. I dropped it at the dealer to take a look and they said it has run great for them. Freeze frame data though showed some o2 readings off. Pass side upstream o2 reading was off and they said that can cause it to over fuel. Both rear o2 readings were out as well. They want to replace all 3 but said you could start with front only. Want 270 for front o2, diagnostic and labor. 

 

Does this sound like it could be the issue? I have not really heard of intermittent o2 issues. In my past experience they were good or bad and threw an o2 code.

 

Thanks,

Josh

Justin101714 Enthusiast

Justin101714

Posted
Posted

You need to find out which cylinder has the most misfires first. If one cylinder isn’t significantly higher in misfires than the other, I would look at O2 readings while burning 87 octane. Make sure the vehicle is warmed up and in closed loop before checking.

 

 

Sent from my iPhone using Tapatalk

 

jrob56 Enthusiast

jrob56

Posted
  • Author
Posted
11 minutes ago, Justin101714 said:

You need to find out which cylinder has the most misfires first. If one cylinder isn’t significantly higher in misfires than the other, I would look at O2 readings while burning 87 octane. Make sure the vehicle is warmed up and in closed loop before checking.

 

 

Sent from my iPhone using Tapatalk

 

They said on 4 and 8. Its just odd they cant reproduce if that sensor is bad. I feel like they are throwing parts at it, and want 90 for diag, 120 for the o2, and 60 labor and taxes. That is almost 3x what the part seems to be online. Think Im going to get it back and drive it some more. Going to have to pay that stupid 90 diagnostic anyway though..

 

https://www.rockauto.com/en/moreinfo.php?pk=6309813&cc=3294345&jsn=12&jsn=12

 

 

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