2005 Chevy Cobalt Car Idol issue

2005 CHEVROLET COBALT
65,000 MILES • 4 CYL • FWD • AUTOMATIC
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SBUTLER
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I have looked on a million sites to see what the issue is with my Cobalt, for about a month now it has been driving really ruff, It starts out fine, and drives fine untill the temp gets to the normal 180 degrees, then when i stop at a light the rpm's go down from 700 to 500 and dip quickly up and down from 200 to 300 back to 500 and then it dips down and stalls the car. No check engine light therfor no code. Dealer says nothing is wrong. So everytime I stop the rpms go up and down fast till the car dies. There are lots of people complaining about it but no answers to why and I dont have money to just replace things until it works.. Please help any advice would be useful.
Thanks, Sheena
Jan 9, 2009 at 3:55 PM
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BRIAN 1
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did the dealer reference this bulletin: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. see if this helps or fixes it,post back with what you find or any other questions.
Jan 9, 2009 at 4:54 PM