2005 chev cobalt sputters at idle. Replaced knock

Sounds like your spark plugs need replaced. ( long shot answer)

pinging is from spontaneous combustion ( detonation) and is from incorrect air /fuel ration and ignition timing. Run fault codes and check knock sensor and MAF/MAP/VAF sensors . Left un- checked it will melt holes in the pistons.

Could be a dirty throttle body, faulty idle control valve, or a vac leak. Usually if the idle control valve fails the check engine light will come on.

As far as the cobalt, check tac/throttle actuator control. Below is circuit description for p1682.
The other codes was for knock sensor.

my 2005 chevy cobalt is having same problem- sometimes even turn on car and it will not go anywhere as if it has no gas---- needs to have o2 sensor replaced...see if that helps yours!

first check the throttle plate for carbon build up the look for the knock sensor harness rubbing onto the fan shroud

There are 3 different engines available for 2006 Chevrolet Cobalt. [ L4-2.4L VIN B, L4-2.2L VIN F, L4-2.0L SC VIN P ] You will probably get a much more accurate answer to your question if you would take the time to mention WHICH of these engines your vehicle is equipped with.

Do not replace with Autozone knock sensors unless you feel like doing the job twice as I found out the hard way. I replaced mine and a week later the check engine light came back on. Went to the dealer and was told they have seen this problem many times before and to use oem replacement parts only. The two sensors and harness ran me about $230 from the dealer but no more engine light and no more sputtering. Hopefully I can return them to Autozone as soon as I find the receipts.

Most likely bad injectors, is the check engine light on?

Fault with the IAC valve.there maybe a trouble code associated with it also./ Go to your nearby autozone or auto parts retailer and ask them to put a scanner to the car....make note of the codes if any are found. the IAC valve i usually locate don the throttle body and can be removed for inspection and sometimes cleaning using a good throttle body cleaner spray and a pipe cleaner brush.