Intermittent high/low RPM's

Hello,

This sounds like you could have a vacuum leak. A vacuum leak will cause a high idle or a "searching" idle when the engine will rev up and down like it's surging. Here is a guide below explaining how to find a vacuum leak in your vehicle:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please go through this guide and get back to us with what you find out.

Thanks,
Alex
2Carpros