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My 2009 cobalts rpms will shoot up and while driving under 35 it sometimes does this herkie jerky thing I've had a complete tune up replaced the camshaft position sensor the intake and exhaust variable timing selinoids and maf sensor it doesn't do it all the time and never at the mechanics any suggestions.
 

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So even though you're holding steady throttle, it feels like it's surging a bit? Yeah, pretty common. Not sure what causes this, but it's harmless.
 

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Unfortunately this is very common with the Cobalt with the automatic transmission. In fact, it’s common on all cars with the 2.2 and 2.4 Ecotec with the 4T45e automatic transmission. Most of the time the RPM surging happens once the vehicle gets some miles on it, but I have driven rental cars back when these cars were new and some of them had the RPM surging with low miles.

As to the issue? No one really knows. The official word from GM is the TCM adaptive learning gets corrupted. Why it gets corrupted is anyone’s guess. The unofficial word is the adaptive learning gets corrupted when the vehicle is driven too lightly. Basically drivers who accelerate slowly often tend to have this issue. GM software engineers were aware of the issue but they never issued a software update, GM says the RPM surging doesn’t affect the durability of the transmission.

One thing you can do to help resolve the RPM surging is keeping the engine tuned up. GM issued a TSB years ago about RPM surging and carbon buildup. GM says to do a top engine carbon cleaning. Carbon buildup in the cylinder head can alter the calculated load percentage that is critical in transmission performance.

I’m not even sure if this is your issue. Regardless, it’s good info for everyone.
 
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