Random knock at cruising speeds

[Kevin 1G Drummer]

It has been doing it on and off since about the middle of last winter. Seems like it will happen intermittently for a couple weeks, then not happen at all for a month or two, then it comes back intermittently again. Last night on my way to work it did it probably 8 or 9 times in a row over the span of about 3 minutes, but then on the way home it didn't happen at all. I will try replacing the knock sensor and see what happens.