09 Cobalt XFE manual. I've had the car 2 years and think it's done it the whole time. But realized it went away this winter, back first day air temps broke 50f it did it again on the way home. Temp colder it went away.
Symptom: driving along light load 1500-2000 rpm, it stumbles for a fraction of a second, comes back on then repeats, sometimes just one, other time 5-8 times. No CEL. no codes via Scan guage. About 85,000 miles now.
It's more than a single misfire it almost feels like you hit a dip in the road as it's enough to slow the car. It's a drive by wire car.
When it happens in 3-4 gear 35 mph it really chugs, at 55 mph its just a dip by comparison. 90%+ of my driving is 55 mph.
I have doubt is cutting ignition or fuel alone would chug like it does, it's almost like the throttle is slamming shut and reopening. The SG2
display doesn't seem fast enough to catch what's going on.