You don’t always have to ratchet up the tension in your novel through action. Dialog, internal dialog, silence, sentence structure and even word choice can boost the tension. (You can say the carousel horse was impaled by the pole, for example, rather than stuck on it.)
Pick a page of your work in progress at random and find five ways to add tension.
Repeat. Again. Do this for ten pages a day and you’ll have increased the tension throughout your manuscript in a month.