From GM:


Owners of 2006 Cobalt SS Models equipped with the Cobalt Performance Accessories Stage 2 Kit may experience an intermittent idle surge, "Service Engine Soon" light, and DTC P0507 set in the vehicle's PCM.

A revised calibration is currently being developed and is expected to be available to all GM Dealers on 09/04/06, as well as be included on TIS CD #9.

 

My idle is allways high when I have used it over a day. It sits at 1300rpm and slowly comes down to 950 then I take off. Allways the same.

 

never had an issue...

 

Nobody else has this? I thought it was normal.

 

On my SS SC when you are coasting in neutral coming to a stop the idle sits at about 1300, and slowly comes down to about 800 when you completely stop. This is all OEM no stage kit yet...

As far as the idle surge, i have had that happen also, and again everything is stock. There is like 1800 miles on the Cobalt, and it has maybe done it 3 times?!?! The idles bounces from 500-1300 RPM, like the IAC (Idle Air Control) is moving to fast. Not sure with the non throttle cable setup if there is a need for an IAC as it can open the butterfly... but just a senerio of what it seems like.

 

Here is a TSB for LSJ Fluctuating, Unstable or Incorrect Engine Idle maybe it will help.
TSB #06-06-04-039 B
2005-2006 Chevrolet Cobalt SS Supercharged
2004-2006 Saturn ION Redline
with Ecotec™ 2.0L I-4 Engine (VIN P -- RPO LSJ)


Condition
Some customers may comment that the engine idle may fluctuate (idle roll) a hundred rpm for several seconds when the engine is started hot or cold. Further diagnostic investigation with a scan tool may not reveal the cause. No other driveability or performance concerns may be reported.

Cause
The most likely cause of this issue may be that the engine calibrations need to be updated to correct the fluctuating engine idle .

Correction
DO NOT replace the throttle body, the ECM or any other parts.

Reprogram the ECM with the latest calibration. This calibration, or any that follow, is designed to address this fluctuating engine idle concern. Refer to Service Programming System (SPS) in SI for reprogramming procedures. As always, make sure your Tech 2® is updated with the latest software version

 

I haven't experienced these issues, but with my newly installed Stage 2 kit I notice that it takes longer for the RPMs to drop after I clutch in and gas out to change gears.