Clever way to check for vacuum leaks?
I've been chasing an idle surge problem for a few weeks now, although it's hardly been a priority. It's gotten cold out here in NH and I feel like it is related to the temp, but can't say for certain. The car starts normally and idles perfectly cold, then after a short drive e.g. to work, when I clutch in the idle fluctuates from 500 to 1000 and back about 8 to 10 times and then settles down to 700ish, and stays there.
I have cleaned the DISA valve and ICV and replaced both intake boots. The ICV in particular was quite dirty, and the lower intake boot was definitely cracked, but the problem is more or less exactly the same.
My research has pointed me to look for vacuum leaks, but other than visual inspection of the hoses I can see, any thoughts about how else to pinpoint a possible leak?
Thanks in advance.