As you've probably already read, replace the knock sensor****! The one part I had the most trouble with was removing the knock sensor wiring harness/connector/clip, whatever you want to call it. I couldn't see it snap onto the sensor. Turns out the button to unbuckle the seat belt was on top (where I couldn't see the car from below). What you need to do is pry the connector away from the sensor with a flat head screwdriver while using your hand (and by that I mean any fingertips you can reach) to press the clip. I will include some photos of what I have in mind. The first image shows what the clip looks like and the second image shows what needs to be done to remove the clip/harness. A NOTICE. The pictures are not actually the knock sensor harness clips but they look the same and show what you need to do to remove them.
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