Have a 2012 GS M6 that just went over 60K miles. Over the past few months, i thought that the engine seemed to be running ever so slightly rough. It didn't feel down on power, there was just the occasional lumpiness at idle. i thought my mind was playing tricks on me to be honest.

Changed the spark plugs today and the #5 plug was missing the electrode.

Plug on the right is a 41-110 and the plug on the left is a 41-162. According to the parts guy at the dealer, the 41-162 is the correct plug for my VIN. Running silky smooth now.

Can anyone help me understand the circumstances that would caused this? The lost electrode that is?

Thanks!

 

I've seen detonation/pre ignition do crazy things to spark plugs. If your engine is stock, I doubt that's the case. Maybe just a bad plug from the factory. It happens. If the others look OK, just change them out and enjoy your Vette. Probably nothing to worry about.

 

Looks like a lean burn on that plug. Might was to check that injector.
I melted an electrode on my SC’d car a couple years ago. I attributed it to bad gas. Car is tuned for 93 and used a station I didn’t trust and the octane was lower then 93. Racing a Gallardo on a very hot summer day and that was it, knew something was wrong right away. I did win the race but was done for day till I got home and changed them all out.

 

Ditto with this, and when was the last time you cleaned the Maf sensor?

 

Thanks for the input gents. All the other plugs were fine. I've just never experienced a plug that burned down like that.

Just got back from a 30 minute drive and she's running great now.

 

Yep. I've experienced that before. In mid-Nov 2014, I was running 10.9's @ 125 on a 1.51 launch in 1200-1400 DA in Phoenix. About the same time I also started having an occasional backfire on the street for a few weeks and then it stopped. Fast forward to Jan 2015 in Sacramento with neg 500 DA and expectations/hopes of squeaking out high 10.6's @ 126-128, since a couple years before (2011), I had a best of 10.82 @ 125,82 on a 1.58 launch in neg 750 DA with Z06 manifolds and a 3600 stall vs the then current LG headers and 4000 stall. However in 10 passes I couldn't put a good launch together with a strong back half. The best 60' at 1.51 had a 10.85 @ 124.19 and the best ET 10.80 @ 126.84 had a 1.54 short time. It just felt like I was starving for fuel either on the first 330' or the last 330'.
A couple days later back in Phoenix, I decided to pull the plugs and found 7 out of 8 had lost the iridium tips. I put in new 41-110's and a week later clicked off several 1.48 launches with 10.8's @ 126+ mph passes in 1400 DA. It just runs better with a .040 plug gap than a .080 gap. I just wish I had investigated the backfires and changed plugs before driving 800 miles to race in CA.
It looks like the tip design on the 41-110's has changed in the last few years. The tips on my current plugs (about 2 years old) are cones vs the stepped cylinders on your new ones. Maybe the pointed cone created abnormal heat by having the spark too concentrated vs an opportunity to have a larger surface with edges on the top of a small cylinder. It's one more change in the evolution since Albert Champion's original design became the adopted standard over a century ago.

 

My spark plugs look just like that and they were only burnt like that from one cylinder. All the other spark plugs were just fine. My question to you is, after replacing them, did you have any other issues down the road, like needing to replace fuel injectors, or did it continue to run perfectly fine after the fact?

 

Double Iridium?
Double Platinum?

 

The spark plug on the left is a hotter plug. The higher the porcelain determines the heat range.