Whats up people! This video is a How to possibly fix your rough idle problems,. My daughters car had a rough idle and a P0300 code. p0300 code is a random misfire code but it doesn't tell you exactly why. So to fix this you have to step by step go through and check all things that could be causing this misfire. The car i'm working on is a 2006 Chevy Aveo and i started by checking the plugs, wires and coil, these were not expensive so i just replaced them. when i replaced them this helped the problem but didn't fix it totally. after that i checked for vacuum leaks and cleaned the egr valve and iac valve, after cleaning the IAC valve i tested it to see if it worked and the valve came apart so i had to replace it with a new one. after installing the new one the rough idle is all cleared up and the car is running well. In conclusion i do not feel that the Iac was the main reason for the misfire but it did add to the problem. By doing all the things above which consist of a tune up and replacing a few things my rough idle is gone. I hope this helped anyone out with a rough idle that might not no why you have it or have a p0300 code. Thanks for watching and don't forget to like and subscribe !!!