Spark plug issues!!!

[OR VietVet]

I apologize about that. I edited the post and included all the information of the vehicle. I was replacing the plugs and wires because they have never been replaced since the car was bought. The first ones were a-premium spark plugs and wires, and then I bought the NGK IX Iridium Spark Plugs 7397, and then the Duralast Silicone Spark Plug Wire Set 4713. There is no other codes at all.

Correct application for the NGK iridium plugs. You bought the cheapest set of AZ plug wires and likely made in China. These trucks like quality parts. I would have chose the AC Delco wires, 748HH, or Delphi wires, XS10389 or NGK wires, 51033 or 51430 depending on ignition coil design. You want another 100k miles out of the plugs and wires and I would not trust Duralast wires for that long. Plus, right out of the box, the wires are suspect. Or, you need to recheck your work and see if you did something incorrectly. DID you use Dielectric grease on the wires during install? You did not say.

P0300 is "multiple misfires on multiple cylinders. WHY?

 

[cmyoung2007]

I did not use dielectric grease on the spark plug wires this time. The Tahoe has almost 300,000 miles on it. It’s sitting at 298,600 right now.

 

[Scottydoggs]

did you use a actual plug socket with a rubber insert? or just a normal socket? if you used a normal socket you might have cracked the porcelain part of the plug/plugs. thats a instant misfire. if ran for a while cracked you'll find it easy due to the black line inside the crack.

 

[cmyoung2007]

I used a Hart 5/8 spark plug socket.

 

[cmyoung2007]

Could it be a coincidence that all of my ignition coils failed?

 

[OR VietVet]

Could it be a coincidence that all of my ignition coils failed?

That is why I asked about what else you may have disturbed or unhooked for access/clearance. If you messed with/moved/unhooked a ground wire, that could explain a code for multiple cylinders misfire. By the way, do a quick fuel pressure test. Easily done at the rail port.

 

[cmyoung2007]

I didn’t move or unhook anything except swap ignition coil one and two to see if the misfire would happen and to see if it was a cause because of that. They have been moved back since then.

 

[cmyoung2007]

I am watching the misfire count as I’m driving, and the only cylinders that aren’t misfiring are seven and eight.

 

[Doubeleive]

I am watching the misfire count as I’m driving, and the only cylinders that aren’t misfiring are seven and eight.

swap 7&8 wires to 1&2 and see if anything changes

 

[cmyoung2007]

swap 7&8 wires to 1&2 and see if anything changes

I took a video, but it won’t let me upload it. Are you talking about the coils?