Persistent Misfire cylinder 3

[Nap73]

Ok, With the coil swapped, the mechanic should have hooked up his bi-directional scan tool and verified that all ignition control circuits displayed OK. This means that there was no Short To Ground, Short To Open or Short To Volts.

If there is, fix the wiring. If all is ok with wiring, replace the ECM.

If the engine runs too long like this, it could take out the cats.

Everything looks fine with the scan tool. Before the ignition coil swap & after. And the misfire isn’t happening all the time. I ran a couple of 20oz bottles of Techron complete fuel system cleaner and took the truck on some longer rides. And it seems to be helping the situation as no codes or “pending” codes showed up until today. I’ll clear them and run some more of the cleaner thru the system. But to me it seems like an injector issue. Just out of curiosity why go straight to the ECM?


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[wjburken]

I go to the mechanic today and he moves the coil from cylinder 3 (the one that was changed ) and exchanges it with the cylinder 1 coil.

You could swap the #3 injector around with the #1 injector and see if the issue persists.

That’s exactly what was done.

You said he swapped coils... you didn't mention he swapped fuel injectors too.

Did your mechanic swap the Coil or the Injector or both?

 

[swathdiver]

Everything looks fine with the scan tool. Before the ignition coil swap & after. And the misfire isn’t happening all the time. I ran a couple of 20oz bottles of Techron complete fuel system cleaner and took the truck on some longer rides. And it seems to be helping the situation as no codes or “pending” codes showed up until today. I’ll clear them and run some more of the cleaner thru the system. But to me it seems like an injector issue. Just out of curiosity why go straight to the ECM?


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Because that's all that's left when you run through the shop manual. That P0353 is a specific code for a coil, not an injector or anything else. You eliminated the coil by swapping it and presumably the wiring has been thoroughly inspected and tested so all that's left is the ECM.

 

[Watonga68]

Mine ended up being a bad lifter in a 2016 Yukon XL with only 52K on it! P0307 in No. 7. Praying that is not your problem, as mine will be covered under the powertrain warranty.

 

[Nap73]

Did your mechanic swap the Coil or the Injector or both?

Miss read your post Man

He swapped coils not injectors. Coils are an easy swap the injectors now that’s a different story. If I’m going that far I’ll just replace them all then.


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[Nap73]

Because that's all that's left when you run through the shop manual. That P0353 is a specific code for a coil, not an injector or anything else. You eliminated the coil by swapping it and presumably the wiring has been thoroughly inspected and tested so all that's left is the ECM.

Got your reasoning. So if it was an injector issue there would be a specific code ? Also I found a ECM for $220 on Amazon. How involved is this to instal ? I’m assuming a dealer needs to program or flash it for your specific vehicle. The explanation and info is appreciated.


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[Doubeleive]

Got your reasoning. So if it was an injector issue there would be a specific code ? Also I found a ECM for $220 on Amazon. How involved is this to instal ? I’m assuming a dealer needs to program or flash it for your specific vehicle. The explanation and info is appreciated.


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I wouldn't jump to replacing the ecm unless all other parts checked first, the ecm is the last resort and yes it would need to be flashed. you would be better of investing the money in a tech2 then you can have dealer level diagnostics in your own hands and it would only cost you $40 to flash the ecm yourself if it came down to that, the tech2 will pay for it's self over time.

 

[Nap73]

Ok so I ran 3 bottles of the Techron fuel system cleaner thru the truck one after another.

1st bottle in a tank less than 1/4 full.

2nd bottle on an almost empty tank that I then filled with 10 gallons of gas

3rd bottle on an almost empty tank that I filled with 10 gallons of gas

After the 3rd bottle I filled the tank.

I had to take an hour and 15 min drive yesterday. No check engine light. When I got to my destination there were 2 pending codes P0303 & P0353.

I then drove an hour and 1/2 home and when I arrived and checked the codes were gone.

Am I correct thinking that my issue is a fuel injector ?


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[wjburken]

Ok so I ran 3 bottles of the Techron fuel system cleaner thru the truck one after another.

1st bottle in a tank less than 1/4 full.

2nd bottle on an almost empty tank that I then filled with 10 gallons of gas

3rd bottle on an almost empty tank that I filled with 10 gallons of gas

After the 3rd bottle I filled the tank.

I had to take an hour and 15 min drive yesterday. No check engine light. When I got to my destination there were 2 pending codes P0303 & P0353.

I then drove an hour and 1/2 home and when I arrived and checked the codes were gone.

Am I correct thinking that my issue is a fuel injector ?


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P0353, as James stated, is a coil specific code. Your mechanic swapped coils and it stayed with #3. I think you stated that the mechanic even swapped injectors and it stayed with #3, but that wasn’t clear. I would make sure I have thoroughly checked the wiring harness going to your coils to make sure they don’t have any corrosion or possible loose connections or damage before going any further. If that checks out, then as the others have indicated, you will need to deal with your ECM.

 

[Burby]

Mine ended up being a bad lifter in a 2016 Yukon XL with only 52K on it! P0307 in No. 7. Praying that is not your problem, as mine will be covered under the powertrain warranty.

Question - did the dealer go right to the lifter or was this found after doing multiple other diagnostics? How did they get to the lifter being the issue and how much did the diagnostics cost before finding the issue?

I've got a misfire on cyl 8. Tried sraying a can of seafoam into the intake and it only somewhat helped. 40K miles on a '16 Next step is taking it to the dealer.