I have a 2006 cobalt ss, 2.0 lsj, in 4th gear around 3500 rpm the car seems to "buck" almost as if the fuel is getting cut off or its hitting redline, i went through all gears except 5th, cause doing that would mean going over 90mph and I was driving at night on a road known for police to be patrolling, and it only happend in 4th. it was raining at time it happend. Not sure what could be causing and I'm not yet fully knowledgeable about these cars. If you guys know anything or know any possible causes please help.

 

Is this during wide open throttle? Sounds like it, since you mentioned cops. If you're bucking at WOT then you're probably feeling torque dips from misfiring when a cylinder or cylinders starts dropping out, as in the combustion isn't pushing down on the piston to give you torque. This could be a fueling problem (too rich, too lean) in a cylinder or cylinders around 3,500 rpm, spark plug blowout is another common cause of misfire under high boost. I've felt something similar when I first got my car tuned by a noob, at around 3,000 rpm the AFR was 9.5:1 super rich, it would break up and lose a lot of power even though you're foot is to the floor.

 

It wasnt as much WOT as just acceleration, and I went there again today when it wasnt raining and it didnt do it, but I wasn't acceleration as aggressively. When It happended last night I was passing someone so It was more of a little over half throttle

And if it is running rich should I change from 93 to mabye 91 or 92

 

Is this a modified car? You should probably go through the engine and look for anything wrong like melted wires, cracked pipes, rotted hoses, etc etc.

Can you hook up a scan tool and check your codes? You should watch the bank 1 O2 signal to see what it is doing also. If you're lightly accelerating then you're probably in closed loop, so the O2 should be flipping. At this point it could be so many things I am probably on the wrong track with the diagnosis because it's challenging to diagnose machines with 5 sentences of information, not your fault it is the way of the internet.

 

If it's dependent on rain you may be getting some water in your intake, seems like a common issue on LSJ's depending on their intake setup