idle problem??

[03silver8g]

Somtimes when driving or stopped it will idle weird and the rpm"s will drop and rise back up.. it kind of hesitates. i did replace my plugs because one was cracked and it was running on 3 cylinders and would have a random missfire. ever since then it would idle wird like i said above.. idk what the problem is!! thanks for your guys help!

[galantlvr34]

it kind of sounds like you might have some kind of vacuum leak or your iac is bad.