I'm just going to answer the question out of my head, using my intuitive knowledge as a native US speaker. In the context of driving, "tooling along" is an informal, stock phrase. It means driving in an easy, relaxed, carefree way, enjoying the ride and not thinking much about it. You could also say "breezing along." I have no idea why the word "tooling" is used, or what relation it has to any other meaning of "tool." A perfect definition of "tooling along" is given by the theme music and typical opening scene in an old TV series called "Route 66." These people are tooling along the highway in their convertible. https://www.youtube.com/watch?v=TZEJ5Oc-B9w Y ahora que te he dado una definición, por favor dígame, como habrías decir "tooling along the highway" en español?

I think Dan Smith was right, at least it makes sense in the story I was reading.

Could it be 'tootling along', maybe? I haven't heard 'tooling along' before..