I noticed something strange about the way my car was running a while ago, it kind of lurched and then when I let off the accelerator it would stay at that rpm for a second and then drop. So I put it in neutral (i know very unsafe driving) and it was going up and down from about 2000 to 3500 rpms. I shut the engine down and restarted it and the problem went away. But now it's doing it every time I go freeway speeds. I wouldn't bother too much with it but it seems to have some effect on the brakes, I push the pedal but it feels like I'm hitting a squishy wall and there's barely any braking effect going on. Any ideas folks?

 

Year? Model? Engine?

 

Oh shoot I forgot to add that haha sorry 2007 mazda3 2.0