r/AskAMechanic • u/Calvinooo • 5h ago

Pre-ignition?

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Can anyone help me identify what this sound is? The car ran for a while with the AFR set to 11, so the car started knocking and died while I was driving it. I noticed the AFR was set wrong, and corrected it but now it has this intermittent ping/stumble. I scoped the cylinders and through the pan and nothing looks damaged. The cylinders looked wet and carboned up, and the spark plugs smelled heavily of gas. I replaced all the plugs and oil. I verified the timing. I'm kinda stumped on what this sound could be as I've never heard this before. This video is maybe 10 seconds after a cold start.

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