p0306 code cylinder 6 misfire

[rclinton]

Read all posts and surfed the internet for some help. Posted in an old thread but wanted to get visibility here. As the title stated driving home got the CEL and ESS lights. Car running rough. Swapped #4 and #6 coil pacs and wires. Puta. Ew plug in number six. P0306 code cleared but came back after a bit at above idle RPM. I have seen other post but no resolution. Hoping there is a fix out there somewhere. Thanks in advance for any insight

[chevybernie]

I had the same problem last year. After kickdown ,when i passed a truck, suddenly the engine light and ess came on. Engine stottered. With every litlle bit acceleration, the ess light came. I looked, take all plugs out and on 2 ignition cables have been a little white , - like powder outside. They had been near the headers. I changed the spark plugs and all ignition cables and all was ok. ( I hope, you understand. My english is not so good).

[rclinton]

I had the same problem last year. After kickdown ,when i passed a truck, suddenly the engine light and ess came on. Engine stottered. With every litlle bit acceleration, the ess light came. I looked, take all plugs out and on 2 ignition cables have been a little white , - like powder outside. They had been near the headers. I changed the spark plugs and all ignition cables and all was ok. ( I hope, you understand. My english is not so good).

English was great. Already bought the plugs and wires. Guess it’s time to roll up the sleeves and get a little dirty.

[rclinton]

Update. Changed all plugs and wires. Still got the P0306 code. Is the next step a leak down test?

[69project]

Yes, you can do a leak down test and see what it says. Don't be that concerned if the leak down is 20% or less. If it's more than that figure out where its leaking from. I had the same issue on my LS3. I did the leak down test and it was greater than 40% on a couple of cylinders, and was leaking through the intake. I would also consider buying a remote camera before you do any removal of the heads or engine to see the inside of the cylinders. I did that with mine and saw some slight scoring on the cylinder walls.

I ended up pulling the motor and found a lot of grey sludge in the bottom of the pan along with a chunk of metal. My heads and valves looked fine, the tops of the pistons look fine as well. I pulled the #8 piston out (it had the greatest amount of leak down) and it looks fine other than the coating on the piston skirt is wore off and the rings don't spin inside their grooves. Some very light scoring on the cylinder walls. 75k on my motor. Something on the inside was eating itself. I have not figured it out yet other than I need to rebuild my engine. I have delayed working on things until my career transition and finances are stable enough to spend money on go fast parts. Not sure how I am going to go with this project because it appears G8 specific parts are getting hard to source. No issues with mechanical bits since they stuck that LS3 in Camaros and Corvettes.

[rclinton]

Just a follow up to close this thread and provide feedback. Number 6 lifter froze and wiped out the cam lobe which then sent metal into the oil and damaged the bearings. Bottom line. DoD delete kit, bigger cam, oil pump, valley tray, lifters, new springs, headers, gasket set. Basically a new rebuild of the engine. But my mindset was I couldn’t buy a car that looked like my G8 with a new engine for the price of a rebuild

[DougT]

Thanks for posting your results! The same code just came up on mine.