As the title says.. the engine is surging when in idle. To give some vehicle context - 1985 Berlinetta with a 2.8L v6.
Every once in a while it'll surge up to around 1700 or so then when it goes back down it stalls out. If I give it steady gas it stops surging. The surging is also intermittent. If it hasn't run in a while it doesn't happen either. But if the engine is still hot it tends to do it more often.

From what I've read, it could be a vacuum leak. I've heard the soapy water trick works reasonably well for this problem in finding where it is. Any other ideas that may work better?

Also, can I get a schematic or something on how the vacuum lines are run? I'm new to the car game so keep that in mind.. Thanks!

 

I used starter fluid to find my leaks.

 

That makes sense. Spray on the vacuum lines and if there's an increase in power there's a leak.

I'll have to try that out. I'm sure I need to be mindful where I spray?