I did some work on the car over the weekend, replaced the plugs and changed the oil. I started it back up after the oil change and I heard a low somewhat popping sound when the car is in low rpm. It may be doing in higher rpm's as well I just can't hear it over the engine noise. I'm not exactly sure when this started since everytime I drive I have my music on and can't hear anything anyway. It sounds like it pops every 4-5 seconds. Can anyone help me out?