Although it's a CPU issue, a heapdump could still be useful. There are ways to do it, such as
https://www.npmjs.com/package/heapdump. You can try to get a dump once the CPU goes up and simply load it into Chrome dev tools - to see what is going on, perhaps there's a hint.
If while at 100% you can't get a dump, you can try doing increments, like every ten seconds or so and then see what changed closer to the problem.
Even better would be if you could run with debugger directly -something like the new `node --inspect server.js`, but that depends on where your servers are, how you run them etc.