Pacing as a writing term is all about the experience for the reader. The Tasmanian Devil approach leaves readers in the dust, and Slowpoke Rodriguez (Speedy’s brother) covers them in cobwebs.
To slow down the pacing, here are good methods:
Add description and details — but not unnecessary ones. You can focus on sensory items (i.e. touch, taste, smell, sound) that serve to make the section a fully immersive reading experience. This might include approaching the action as if it’s in slow motion. I took this route at several points within my memoir-in-progress where the action was chaotic or ominous.
Add dialogue — but not filler. Body language counts. Even just a sentence or two can reveal character motivation or inner thoughts/introspection/decision-making, or perhaps emotional conflict can highlight other plot points. Aim to develop the section gradually.
If you run out of useful things to add, you can also play with your sentence structure and syntax, favoring longer sentences and more complicated clauses.
To speed up, try these:
As the great Strunk and White adage goes, "omit needless words." Trim every extra word and phrase possible. Shorten descriptions and details to just what’s necessary and vivid. Assess your descriptive and reflective passages for unneeded backstory or exposition. Either move those sections somewhere else or cut them completely. In their place, include action. By emphasizing dynamic elements, the pacing will increase.
Try introducing a deadline. This could take the form of a new complication or stakes-raising or foreshadowing a future ominous outcome. Focusing on reactions instead of the larger questions of “what they mean” can also make the pace quicken. This is also a good place to consider if you can just jump ahead in the narrative, trusting your reader will follow.
And, of course, shorten those sentences. Make them simple, i.e. subject-verb construction. Use fragments. Choppiness alone makes a passage read quickly.