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changing misfires

HawkMTP

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HawkMTP New Member

HawkMTP

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Hey guys I have a 2014 Silverado 5.3L.  After a recent service at the dealer here in Hawaii my CEL came on.  I took it back in it was a cylinder 7 misfire.  The dealer replaced the wiring harness and the #7 coil pack.  Brought the truck back home light came on again.  Used a friends code reader and had a cylinder 5 misfire.  last night replaced all the plugs and noticed the #5 wire came right off the plug when I removed the coil pack.  Today truck is running rough and now I have another intermittent CEL between solid and flashing for a cylinder 4 misfire.  Plugs looked fine but replaced them anyways.  Anybody have any idea what is going on.  This truck on has 65,000 miles on it and has never had any problems until after the service.

Supreme Pizza Senior Enthusiast

Supreme Pizza

Posted
Posted

That's a tough one. Hard to pinpoint it based on those symptoms. What services did they perform at the dealer, prior to this problem? 

 

If I had those issues, I would start with plugs, wires, a bottle fuel injector cleaner, unplug the battery for 30 minutes, check the air filter, and maybe look around for vacuum leaks and disconnected hoses. 

 

What island are you on? Oahu? 

Supreme Pizza Senior Enthusiast

Supreme Pizza

Posted
Posted
45 minutes ago, silveradosid said:

to get that many miss fire codes all of a sudden i would be checking the gas sound like you got a bad tank

 

 

Ya, I was thinking that too, but he was saying it started right after the dealer serviced it. Maybe got gas right after leaving the dealer? I guess you could throw some Heet in the tank to see if it helps. Sometimes gas stations add water to their fuel to increase the profit margin. This stuff would help: 

 

 

 

 

 

 

HEET-Gas-Line-Antifreeze_12oz (1).jpg

HawkMTP New Member

HawkMTP

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So ended up changing the #4 coil pack and now I only get a misfire on #4 when starting clear the code and it goes away and truck runs fine.  Could it be air?  Maybe a PCM issue im at a loss.

Supreme Pizza Senior Enthusiast

Supreme Pizza

Posted
Posted
16 minutes ago, HawkMTP said:

So ended up changing the #4 coil pack and now I only get a misfire on #4 when starting clear the code and it goes away and truck runs fine.  Could it be air?  Maybe a PCM issue im at a loss.

 

 

 Could you describe this more clearly? You clear the code while its running?

TJay74 Senior Enthusiast

TJay74

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Posted

The trucks have had some issues with bad injectors that cause issues at start up. What code are you getting?

HawkMTP New Member

HawkMTP

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Still getting the P0304 code however went out this morning and started it to go to work.  No code but still running a little rough at idle.  Yes i cleared the code with the truck running

HawkMTP New Member

HawkMTP

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MAF looks fine.  People keep saying its dirty fuel or possibly an injector but i dont think an injector would manifest after two other cylinders misfired.

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