Buzzing/Knocking Sound from Engine

[n8marx]

Three days ago my 3.2 developed an odd sound. I had driven it to lunch and got it up to about 1/3 of operating temperature. It then made what I would describe as a "buzzing" noise. Like there was a large bee in my engine compartment. It would only make the noise with very little throttle input at low RPMs. Accelerating or decelerating the noise is not there. Idling the noise is not there. Revving with no load the noise is not there. It still occurs at about 1/3 operating temp but has become a little louder, almost a knock. It sounds like a loud valve ticking but not quite the same. Comes from high up on the passenger side of the engine. I am wondering about a failed tensioner but have not heard anything that sounds even remotely similar to a chain being dragged out of a trash can.

Any ideas?

[n8marx]

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