When I forst start the truck up after it has cooled all the way down it sounds like it knocks. At first it thought it was a bearring but now I am getting positive it is something knocking. But it goes a way after a minute or so. Not long what could this be, and how can I test for more information. Also the knock sensor has not showed a code. If the bottom end knocks will the sensor pick it up or isthe sensor for mostly the top end like when you put bad gas in it and the engine pings and knocks?

 

Depending on your model, it could be the throttle cable slapping against the PCV valve, but on the 98+ models, its just a characteristic of the engine.

 

it is a 96 with the 4.3 V6.

 

Your Blazer falls within the year range of the ones that had that problem... just get a ziptie or something and see if you can secure the throttle cable away from the PCV.

 

Okay I will try that, thanks. I will post again once I get some time on my hands.