This morning going to work I noticed that the engine had a knocking noise to it. The weather has been cold and the noise went away after a few minutes. Could this be piston slap? It almost sounds like a diesel engine. It just turned 6500 miles with no noise issues until now.

 

Hmmm....when was the last time you filled the truck up? Bad gas maybe? Have you checked the oil level?

 

When you said cold and diesel engine, piston slap came directly in my head.

 

For the first few months after I bought my truck I was aware of that same sound. However since I stopped going to the McDonalds drive thru every morning, I no longer hear the diesel engine sound. Same thing with my fan, it revs up and down when cold. But only noticeable at the drive thru. I would not worry about it. I think its normal.

 

mine was doing something similar but it turned out to be a misfire... reflashed the pcm and now its gone... just a suggestion

 

Injectors maybe?