[Tyler Durdan]

It could be an o2 sensor that causing the fluctuation at idle. As for the heater vents, is it that no heat comes out, or no air at all. If it's no air at all, check the vent motor (don't know the exact name of it)...it's electrical. Autozone, or dealer depending if you want to spend the extra bucks for the oem part. Easy fix...takes about ten minutes. It's located at the passenger side near the firewall I believe...that's where they are on most cars, but check under your hood and see if your getting voltage from it. It could also be a blown fuse or short in the wires somewhere, but my money's on the the motor.