Spark plug issues!!! - SOLVED

[cmyoung2007]

I have a 2004 Chevy Tahoe LS 5.3L V8 Flex (VIN Z TYPE), and I just replaced the spark plugs and wires. I’m now having a code being thrown and it is p0300. Does anybody know what the problem could be?

 

[Doubeleive]

I have a 2004 Chevy Tahoe, and I just replaced the spark plugs and wires. I’m now having a code being thrown and it is p0300. Does anybody know what the problem could be?

double check your work, pull the plugs and wires if necessary, look at the plug gap, re-install to I believe 14ft lbs. (might want to verify that, just going off of memory)

 

[cmyoung2007]

double check your work, pull the plugs and wires if necessary, look at the plug gap, re-install to I believe 14ft lbs. (might want to verify that, just going off of memory)

I’ve done that twice now. I bought new spark plugs online. I installed those and it was misfiring, and then I bought NGK’s from AutoZone and it’s still misfiring, but not as bad. The original spark plugs that were in it before all of this was Acdelco Spark Plug 41-110. I did some research on them and it said that those weren’t even a fit for my vehicle, but they worked fine and there was no check engine light or misfiring when they were in the vehicle.

 

[Doubeleive]

I’ve done that twice now. I bought new spark plugs online. I installed those and it was misfiring, and then I bought NGK’s from AutoZone and it’s still misfiring, but not as bad. The original spark plugs that were in it before all of this was Acdelco Spark Plug 41-110. I did some research on them and it said that those weren’t even a fit for my vehicle, but they worked fine and there was no check engine light or misfiring when they were in the vehicle.

did you replace the wires also?
might be a good idea to hook up a scanner and see if you can see where the problem is occurring, (which cylinder specifically), then try swapping things around and see if the problem follows the wire or plug, etc
process of elimination....
p0300 is random, but that also just means it is happening on more than 1 at the same time, could be 1/4/7 so on so forth

 

[cmyoung2007]

did you replace the wires also?
might be a good idea to hook up a scanner and see if you can see where the problem is occurring, (which cylinder specifically), then try swapping things around and see if the problem follows the wire or plug, etc
process of elimination....
p0300 is random, but that also just means it is happening on more than 1 at the same time, could 1/4/7 so on so forth

Yes, I did. I have a foxwell NT809BT scanner, so if you or anybody has any experience with advanced scanners and can tell me what to use on it to find out what the problem could be, I’m all in for it. I’ll upload a screenshot of the misfires here in a little bit.

 

[Doubeleive]

Yes, I did. I have a foxwell NT809BT scanner, so if you or anybody has any experience with advanced scanners and can tell me what to use on it to find out what the problem could be, I’m all in for it.

not familiar with that scanner but they all basically do the same thing, you will want to select engine data, then it should have a misfire monitor or better to monitor live data view

 

[OR VietVet]

Welcome to the forum from Oregon.

You did not say which engine, why you were replacing the plugs and wires to begin with and you did not say which NGK plugs you installed. You did not say which plugs you replaced that you got online and where online. The AC Delco 41-110 is listed as original equipment. If the old ones were original and had never been changed, then they may have been correct plug from the factory. Since you said there was no misfire before this work, then I can only ASSUME that you were doing the work as a maintenance item and because of mileage. How many miles on the engine? If you did not crack the porcelain on the plugs during install and if the plugs you installed are correct for the unknown engine and unknown installed plugs and unknown wires and wires installed correctly and on right coil for correct plug and if use Dielectric grease, then you may have created your problems with something else done during the plugs and wires removal and replacement. What else did you MAYBE unplug or move? A lot of unknowns here. Are you sure the only code is P0300 and no other codes?

 

[Fless]

Use a scanner that can read individual cylinder misfires.

Spark plug torque is 132 INCH lbs (11 ft-lbs).

At what gap are the plugs set and did you have to adjust it before installing?

Make sure the plug wires snap into the coils and onto the plugs. Pop the hood in the dark to see if spark is getting outside of the secondary ignition system.

 

[cmyoung2007]

Welcome to the forum from Oregon.

You did not say which engine, why you were replacing the plugs and wires to begin with and you did not say which NGK plugs you installed. You did not say which plugs you replaced that you got online and where online. The AC Delco 41-110 is listed as original equipment. If the old ones were original and had never been changed, then they may have been correct plug from the factory. Since you said there was no misfire before this work, then I can only ASSUME that you were doing the work as a maintenance item and because of mileage. How many miles on the engine? If you did not crack the porcelain on the plugs during install and if the plugs you installed are correct for the unknown engine and unknown installed plugs and unknown wires and wires installed correctly and on right coil for correct plug and if use Dielectric grease, then you may have created your problems with something else done during the plugs and wires removal and replacement. What else did you MAYBE unplug or move? A lot of unknowns here. Are you sure the only code is P0300 and no other codes?

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.

 

[cmyoung2007]

Use a scanner that can read individual cylinder misfires.

Spark plug torque is 132 INCH lbs (11 ft-lbs).

At what gap are the plugs set and did you have to adjust it before installing?

Make sure the plug wires snap into the coils and onto the plugs. Pop the hood in the dark to see if spark is getting outside of the secondary ignition system.

I made sure the NGK Spark Plugs gap was set to 0.040 and they were straight out of the box.

 

[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?