I have the same darn noise and it drives me nuts!

 

Had anyone found out anything in this noise? Mine is doing it too and can not pin point it

 

Are you absolutely sure you hooked up the knock sensor? Spark knock can sound like a rattle under load.

 

yep, same here. (2000 Blazer 4x4 LT) Not very loud and only under acceleration or load. Sometimes louder and more noticeable, but other times gone altogether. Been that way for YEARS, (306000 miles now). I can sometimes get it to do it in the driveway in gear, foot on the brake and lightly press on the gas. But listening under the hood is still is deceiving where it s coming from... Winter here now in the northeast, but I thought I was hearing it start to come back. Gonna do my 3500 mile oil change soon and see if it makes a difference. I know its a quart low right now.