assuming this is a straight drive. My car does the same. I have tried everything but there is so many things that can cause that. It can be your TPS is what I would check first, then maybe a you IAC. Try those 2 first IMO. Some people on here might disagree with me
See the "Surging Idle Checklist for help with all your idle/stall problems. The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes] for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.