Another P0303
 

2010 SS, 5-speed, 65,xxx miles, no mods (oh - K&N filter in stock airbox)

I've heard/felt a slight miss when warming up the engine over the last few months, so I wasn't surprised when the CEL came on the other morning. P0303 . After being a Good DooBee Forum Member by searching the exhaustive archives here, I was able to remove that blasted airbox (a thread of its own). Then I did what I think Donbrew suggested: I swapped plug #3 with #2 spot, and swapped coil #3 with coil #4. I performed a safe lobotomy at the negative terminal of the battery post, and I'm driving it again, waiting to see which code rears its ugly head.

Will update y'all as this unfolds... hoping it's a bad plug! hahahahahah (i won't hold my breath) I've seen how bad this can turn out... so the truth is I'm hoping AND praying that it's a bad plug.

Yep, you're doin' it right! If it moves, you've got your answer. If it doesn't, you're on to a compression test and maybe a leak down test. Keep us posted.

Doing right! How did the plugs look? Was there any moisture on the coil below the valve cover? Did the coil connections look alright?

Are you over oiling the air filter?

RJ - thanks, you can count on the updates!
Blue - plugs looked normal (but rust developing on ceramic - look like the original ACDelcos); no moisture at all; connections seemed secure from harness AND to plugs
don - i haven't oiled the filter, but i DID look closely at the MAF and plumbing on the way down to the turbo and it was dry (i had cleaned it out of minor accumulation last year when trying to figure out my initial underboost problems)

Thanks for that input guys - and thanks for your support! I told my wife last night (she asked who I was typing to) that there was NO way I could have kept this car going without you guys.

Rust on the ceramic? Do you mean an red/orange discoloration? If it is worse on #3 than the others that could mean coolant getting burned in #3 and causing a misfire.

Original plugs, red like stuff on the coil boot? Mine was the silicone like stuff was discoloured, I wiped and cleaned that stuff off and use silicone grease to lube the boot , that wasn't discoloured when I changed to third set of plugs! I'm only 70,000 miles till my next set!

I think both plugs that I pulled had the same rust-color... but I'm not 100% sure (yes don - exactly: red-orange discoloration). I've seen that discoloration enough in the past that it didn't even trigger a Warning Alert in my (feeble) brain. The electrode-ends looked similar. The coil-boots were all free of gunk or anything... I read LATER that I should use dielectric grease and NOT use anti-seize on the spark plugs. DOH. DOH. I reckon i can clean it off next time.

I wonder how long it will take for the CEL to trigger again. I don't hear the miss immediately upon startup anymore. But after it warms up a little (if I'm sitting in the driveway) I hear it miss after the initial higher-rpm warm up phase. A little strange.

Keep us informed!

What part of the insulator was discolored? inside or outside the combustion chamber?