01 corolla with nocking or puttering idk I need a little advice none of my cars are doing this except my corolla and ive never heard anyone i knows cars make this sound b4 so when im driving i hear what i call a puttering sound its weird it happens when i let off the gas to slow down or try to keep a steady pace of the highway it putters almost likes its starving for fuel but it isnt. now this doesnt happen when it is cold but once it warms up it starts happeing. now idk if its the tranny cause that is starting to slip i think or if it the engine or both. i have 107k miles on it and need a little help it also does it when i drop it into neutral around 2k -3500 rpms then it stops but if i let off it does it. just need some help maybe an easy fix but im betting it isnt im going to take to my mechanic next week so want some opinions on it i am uploading a video to youtube so you can hear the sound.