Idle/High RPM/MPG Problems
ok so i have a 2007 chevy cobalt ls 5 speed. for my graduation project i decided to build a custom cold air intake, since i read a lot of people had completed it succesfully. so i put it on. i also cleaned the top of my throttle body, i didnt take it off the intake manifold but i did spray a rag, and then wipe everywhere i could inside. and yes i moved the part that opens and closes. i put a cone over my PCV valve where there used to be a vacuum line from my valve cover to my intake tube.
-idle feels jumpy, when just sitting there it feels almost as if the engine loses some power for a split second, but then jumps right back, it has vibration when this happens. this occurs about ever 3 seconds at idle
-i have the famous high RPM problem now. if im driving and shift out of a gear and into neutral, my RPM don't drop like they're supposed to. they just stay up. sometimes when i come to s complete stop my RPMs are still around 2500 - 3000 and then they start to fall. i idle at about 1000 RPM
-last, since i did this intake, my MPG has gone down to about 20 - 24 MPG. this is about 3 MPG worse then what i got with my stock intake on.
I HAVE TRIED...
-unplugging both battery terminals for over an hour and a half
-the whole TB "reset" where you turn your key to ignition, not on, for 30 seconds
-i dont have any leaks on my intake, i checked
-Ive cleaned my MAF sensor with the crc cleaner, so its not dirty.
-The arrow is pointing towards the throttle body when installed in my intake.
-I changed my spark plugs
Please if you have any ideas let me know ASAP! this has been happening for about 4 days now. thanks guys, please help me out