Hi guys I hope I can explain this properly. I have a 2000 Mustang GT I don't use the car much maybe 2 or 3 times a month but I start the car every week, what is happening now is when I start the car it runs fine for about maybe up to 30 seconds then the car starts to run ruff for maybe 10 15 seconds then it runs fine after that. I took the car out today to see if the roughness comes back but it did not. I change the Idle Air control motor in Dec 2017. What could be my Issue?