Truck started fine, drove it 20 miles. Then started it again and drove it but when driving after a few miles I would hear a rattling noise coming from under the truck. You can feel it vibrating through the floor. So I parked it and open the hood and I could see the engine wanting to die. You could also see the tensioner extend downward. I shut off the engine and it started just fine but same results...engine wanting to die, tensioner pulling down and you could hear a rattling, grinding noise. I shut it off again and tried to start it again but this time it would not start at all. Engine would turn over, but in a whining sound like trying to start. Battery is brand new, new plugs, rotor and wires....oil changed every 5000 miles with synthetic. My truck only has 100620 miles.
Any one out there that might know what's going on with my truck?
I just filled up the tank with gas as well.
It has the 4.3 V6 engine (NOT 4x4).
Thanks

 

It sounds like a fuel issue. Could be a clogged fuel filter or a faulty fuel pump. Do a fuel pressure check. That will verify if it is a fuel problem.

 

What is the problem You will want to address that as soon as possible to prevent engine damage.Go to a mechanic he will sort it out.