I recently aquired this 2006 cobalt with only 68000 on it and had been sitting for a couple years. I have performed an oil change, new air filter, new cabin air filter, new spark plugs, MAF sensor, and cleaned oit all of the pine needle debris from the engine compartment. I have driven this car daily now and whenever I stop somewhere for a short period of time and restart the car (it's still warm) it fluctuates from about 500 rpm to about 1200 to 1500 rpms. It only sounds like the motor is revving and stops within about 10 seconds. Any ideas? Will be cleaning out the throttle body shortly..