6.2 liter GM with bent spark plug

That plug looks like it has been overheated which may be caused by detonation. Replace the plugs and try it again.

Here's a SWAG (scientific wild-ass guess) is it possible for a carbon buildup ,,, Nah,that ain't possible ... is it?

F_O_R, the pic I showed was when it happened the first time. It was driven that way for a bit as my wife was on a trip. The plug didn't have so much buildup the second time. Tom, that theory has been kicked around, but the thought is it wouldn't build up enough to do that?

I would install new plugs and see what happens. If you are having severe knock then the timing may be off. Are you using premium fuel?

That is kinda the plan at this point. I may try get a scope to borrow and try look in the cylinders through the spark plug hole to see if I can see anything. I am not using premium fuel. I know it is "recommended" on this vehicle. That is something I could try. Thanks

Using the wrong fuel and having a faulty knock sensor could cause your problem.

Is the spark plug the correct part for the vehicle?

Yes, spark plugs are correct

Stick a bore scope into the cylinder and look for excessive carbon deposits. Excessive carbon at the top of the piston can cause a knock and damage the spark plugs. Is this a high mileage engine that uses oil?

Bob, I am currently asking around to see if anyone has a bore scope I could borrow. I was Thinking debris, but will certainly look for carbon as well. It is high mileage (207,000) and it does use oil. Thanks

You can buy a bore scope cheap at Harbor Freight.

Read this article but I still think you are having detonation problems. http://www.onallcylinders.com/2012/12/20/reading-101-how-to-read- your-spark-plugs/

Try using premium fuel and go one range colder on the spark plugs.

Although I would agree with F_O_R that running premium might help, I would disagree about changing the spark plug heat range unless you know exactly what you are doing. It may be time for a Seafoam or similar treatment to get rid of excess carbon on the piston head.

Did you get it fixed?

Bob, I think it is worth a try. Going a range colder won't hurt anything at this point. If they become fouled then go back to the stock heat range.

What was the outcome of fixing it, pls if you have time need more info 3058968674 I'm having same problem out of no were traction light and engine light came on and code reads number 7 thanks Damian

I have a 2013 Yukon Denali XL with the L98 6.2 liter engine. I am having the same issues as well. The stabilitrack traction control lights came on and it runs really sluggish compared to Normal... It also threw an engine code that I haven’t read yet. I know that these engines require DEXOS oil which I didn’t use last time I changed it so I’ve changed the oil with Mobil 1 DEXOS 5W30 oil and added two quarts of Lucas Oil Stabilizer. Drove it afterward and got engine to Normal operating temperature and still does the same thing.

Has anyone resolved this issue. I am having the same issue. Thank you

My issue ended up being a problem with the pistons (although the actual root cause is uncertain...maybe detonation or other ignition issues). Family member is an auto machinist so we removed the engine and rebuilt it. The piston started to deteriorate and pieces would rattle around in the cylinder and eventually blow out the exhaust (sometimes causing damage to spark plug). There were 2 pistons doing this. We found damage to the cylinder and the exhaust valves. Here is the list of work done: bored and honed block to thirty thousands, replaced Pistons and rings, ground valves, replaced one bent exhaust valve, replaced camshaft, replaced lifters. Resurfaced heads and exhaust manifolds. Ground crankshaft. As well as new bearings, seals, etc. In short it was a big job, about $1,000 in parts, but I worked on it with him so no labor. Have about 80,000 miles since rebuild with no issues or engine lights at all. Mine was an extreme case, but I knew that possibility when I purchased it as the worst case would be a rebuild.