P0300, Random misfiring at idle, Counterfeit Spark Plugs?

[donjetman]

07 Yukn Denali 6.2L w/193k miles.
5+ years ago I bought a set of AC Delco #41-962 spark plugs from amazon. 2.5 yrs and 22k miles ago I installed them gapped at .040".
Recently, I've been getting a P0300 code and the engine has had a misfire at idle. It runs great otherwise.
It doesn't set a CEL. I go look for codes with my scanner because of the rough idle. and a 2k+ mile trip we are doing in it soon.
I pulled a plug and its gap was .065". I pulled the rest of the plugs and they were all .065". All the electrodes had worn badly. These plugs have only 22K miles on them. Must be counterfeits.
I went to NAPA and bought 8 new NGK Iridium IX # 7397 ($70), and new wires ($65), installed everything and its purring like a kitten again.

 

[Fless]

Yeah, no way those old ones had platinum tips on them. Glad you figured it out.

 

[Geotrash]

07 Yukn Denali 6.2L w/193k miles.
5+ years ago I bought a set of AC Delco #41-962 spark plugs from amazon. 2.5 yrs and 22k miles ago I installed them gapped at .040".
Recently, I've been getting a P0300 code and the engine has had a misfire at idle. It runs great otherwise.
It doesn't set a CEL. I go look for codes with my scanner because of the rough idle. and a 2k+ mile trip we are doing in it soon.
I pulled a plug and its gap was .065". I pulled the rest of the plugs and they were all .065". All the electrodes had worn badly. These plugs have only 22K miles on them. Must be counterfeits.
I went to NAPA and bought 8 new NGK Iridium IX # 7397 ($70), and new wires ($65), installed everything and its purring like a kitten again.
View attachment 422374
View attachment 422375

Sucks. If Amazon doesn't fix their supply chain for auto parts authenticity, people will stop taking the risk. I have 45K on the Iridium plugs I installed in our '07, purchased at Rock Auto. They're still doing great. I wouldn't buy a hubcap from Amazon.

 

[donjetman]

I knew it wasn't fuel (lean or rich) related because of the live data info on my code reader was normal.

 

[BG1988]

07 Yukn Denali 6.2L w/193k miles.
5+ years ago I bought a set of AC Delco #41-962 spark plugs from amazon. 2.5 yrs and 22k miles ago I installed them gapped at .040".
Recently, I've been getting a P0300 code and the engine has had a misfire at idle. It runs great otherwise.
It doesn't set a CEL. I go look for codes with my scanner because of the rough idle. and a 2k+ mile trip we are doing in it soon.
I pulled a plug and its gap was .065". I pulled the rest of the plugs and they were all .065". All the electrodes had worn badly. These plugs have only 22K miles on them. Must be counterfeits.
I went to NAPA and bought 8 new NGK Iridium IX # 7397 ($70), and new wires ($65), installed everything and its purring like a kitten again.

yeah those spark plugs are fake even the printing on them doesn't look right look at the D then look at the D here

https://www.oreillyauto.com/detail/c/acdelco/ignition---tune-up/spark-plugs/b14eb31b13d7/acdelco-spark-plug/acd0/41962

 

[coreygeoffrey]

2017 GMC Yukon 5.3L 4WD.

BLUF: Only use AC Delco spark plugs and wires!!

For standard maintenance, I changed my spark plugs and wires. Ordered plugs and wires from RockAuto, which I really really like.i ordered the NGK plugs they recommended (I’ve always liked NGK and this is my first GM vehicle) and AC Delco wires with the heat shield. After I was done swapping the parts, I ran it and noticed it started sputtering bad and threw the engine code light with a P0300. The scanner showed number four cylinder misfiring like crazy. I swapped the wire, plug, and coil from a different cylinder hoping the issue would follow. It did not. After reading this thread, I decided to replace the NGK plugs with AC Delco plugs. I disconnected the battery to reset everything. Took it out for a test drive and no issues at all under heavy throttle play. I will only ever recommend AC Delco for any GM products moving forward.

 

[Just Fishing]

I won't buy plugs online unless they are from a seller that I know verifies it's sources.
Summit racing is good, Jeggs, otherwise I go to the local auto parts store for that stuff.

I got burned once, that was enough.

 

[Blackcar]

2017 GMC Yukon 5.3L 4WD.

BLUF: Only use AC Delco spark plugs and wires!!

For standard maintenance, I changed my spark plugs and wires. Ordered plugs and wires from RockAuto, which I really really like.i ordered the NGK plugs they recommended (I’ve always liked NGK and this is my first GM vehicle) and AC Delco wires with the heat shield. After I was done swapping the parts, I ran it and noticed it started sputtering bad and threw the engine code light with a P0300. The scanner showed number four cylinder misfiring like crazy. I swapped the wire, plug, and coil from a different cylinder hoping the issue would follow. It did not. After reading this thread, I decided to replace the NGK plugs with AC Delco plugs. I disconnected the battery to reset everything. Took it out for a test drive and no issues at all under heavy throttle play. I will only ever recommend AC Delco for any GM products moving forward.

AC plugs fix problem and drives fine and you will never recommend again???

 

[kbuskill]

07 Yukn Denali 6.2L w/193k miles.
5+ years ago I bought a set of AC Delco #41-962 spark plugs from amazon. 2.5 yrs and 22k miles ago I installed them gapped at .040".
Recently, I've been getting a P0300 code and the engine has had a misfire at idle. It runs great otherwise.
It doesn't set a CEL. I go look for codes with my scanner because of the rough idle. and a 2k+ mile trip we are doing in it soon.
I pulled a plug and its gap was .065". I pulled the rest of the plugs and they were all .065". All the electrodes had worn badly. These plugs have only 22K miles on them. Must be counterfeits.
I went to NAPA and bought 8 new NGK Iridium IX # 7397 ($70), and new wires ($65), installed everything and its purring like a kitten again.
View attachment 422374
View attachment 422375

Had the same issue....


I think mine were from Ebay but can't remember for sure.


I replaced them with Ruthenium plugs from Rockauto.

For the record, no my Burb isn't some special edition concept engine that takes 12 plugs (although that would be pretty cool) the other plugs are for my Honda.

Not sure how long the Ruthenium plugs will last but they are supposed to be even better than the Iridiums so only time will tell.