2011 5.3 #1 Cylinder

[2011 RG Sierra]

Hello, I'm late to the game on this forum. I've owned my 2011 Sierra CC Z71 for 10 years. I recently changed spark plugs because I had the check engine light come on and the code was "Cylinder 1 Misfire". 7 of the 8 were fine but the #1 spark plug was considerably blacker and oil was in the port. I'm guessing piston rings? Any advice is appreciated. 124k miles on motor

 

[Peterbilttech]

Hello, I'm late to the game on this forum. I've owned my 2011 Sierra CC Z71 for 10 years. I recently changed spark plugs because I had the check engine light come on and the code was "Cylinder 1 Misfire". 7 of the 8 were fine but the #1 spark plug was considerably blacker and oil was in the port. I'm guessing piston rings? Any advice is appreciated. 124k miles on motor

Did you do a compression test on that cylinder and a few others for comparison? Maybe the coil or wire has failed and is not making spark to burn the fuel. You need test results so you'll know which way to go.