Engine misfire

Have you checked fuel pump pressure? This guide is great for finding misfires

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down this guide and report back.

Actually, I am a woman that doesnt know one thing about cars. BUT.. this has been my truck for almost 6 years. I know when its now running correctlyl At low speeds, fine. Getting on highway, or changing speeds on highway truck hesiates, jerks, bucks. I dont know if mechanic tried the fuel pump pressure. If there was an issue with the fuel pump, would a code come up? No engine light, or code came up when he plugged into computer.

The fuel pump itself won't set a code. If it causes it to misfire for an extended period of time, the misfire will set a code. See if he checked fuel pressure.

OH.. ok great. That makes total sense!!! If fuel pressure is the issue, that that indicated a bad fuel pump?? Or a more serious issue.

Usually it is either a plugged fuel filter or the pump itself

THANK YOU THANK YOU. I will have him check that. Have a good day.