Misfiring number 3 cylinder

[Manq]

Good afternoon everyone,
I have a 2015 GMC yukon denali with a 6.2 L engine that has a misfiring code on the number 3 cylinder. I have checked for spark from the spark plug and the coil, I found no problem, so I replaced the spark plugs, coil, and wires anyway, misfire still is still happening, then I went to the injectors and replaced them and the fuel rail, (do I need to say why I replaced the fuel rail). Anyway I still have the misfire, any thoughts and help would be appreciated, thanks.

 

[lost1wing]

Cylinder leak test. Or verify your injector is actually getting the signal.

 

[Manq]

Cylinder leak test

Thanks lost1wing unfortunately I don't the gauge so I guess I have to ask the dealer to do it (damn,damn).

 

[Fless]

TIP: Save your old parts since you haven't yet found the culprit. Might want to reinstall them if the replacements were aftermarket parts.

 

[Miami-Dade]

@Manq Moved you here from Site News.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

You've been unsuccessfully firing the parts cannon so far, so its time to collect some data. Take the truck to your local auto parts store and ask them to put their scanner on it and see what Trouble Codes exist. That will help us help you resolve your issue.

 

[Manq]

Miami-dade, since i'm new to the tread what does (Moved you here from Site News) mean?

 

[Manq]

Thanks Joseph, I do have a code reader and it shows a P0303, number 3 cyl missfiring that is the only code.

​

 

[Fless]

Miami-dade, since i'm new to the tread what does (Moved you here from Site News) mean?

It means that as a moderator he moved your thread from "Site News" to this one, so it would be in the correct year and sub-section for your issue.

Forum tip: to tag someone first enter the "@" sign, then start typing the member's name. Like this: @Miami-Dade. You can also "Reply" to his post like I did here. Either way he'll get a notice. Otherwise there's a likelihood that he won't see your comment.

 

[intergalactron]

Any update on this one?

Also, does it misfire all the time or only at higher rpms? Could one of your valve springs gone weak?