Today I changed my oil, oil filter, air filter and spark plugs. After I was done I started my car and it seemed normal at first but then I noticed the rpms were fluctuating between 500 to 1000 rpms. It is a very quick fluctuation, you actually have to be in the driver seat to feel it and see it. It almost feels like the car wants or off but it doesnt. It also happens when driving. Anybody know any have an idea of what I might of done wrong?