I've recently noticed, that I have this erratic idle when I'm in gear while trying to stop my car and/or when stopped. Normal Rpm around 600 or 700. When it's erratic it's around 1200 or 1300. It might take 20 or 30 seconds to adjust back to normal rpm after I stop. Here a couple of things I've noticed as well: It takes more brake pressure to stop my car, and I'm also losing fuel mileage.
I don't have an engine light on. Anyone have any idea's what to look at first??

 

Sorry, it's a 2007 Maxima