1995 Sunfire Stuttering Problem

I am so frustrated with the run arounds from the dealers and shops. Noone knows what is going on and just sends me on my way like I don't know what I am talking about. Can anyone tell me if you have experienced this and is it fixable? My car was stuttering and so I took it in to the dealer. When I reach 40 miles per hour that is when it starts to stutter. The dealer ran a diagnostic check on it and said that it was fine and recommended changing the fuel filter. After having them change the fuel filter, my car still stuttered when I reached 40+ miles per hour. I took it back and they said that it was the transmission and it is meant to kick in at 40 mph. I know for a fact it is not the transmission, I just had it looked at a couple of months ago. I have never had that problem before where it would stutter then it run smooth and then stutter and then run smooth. I am afraid it is going to die on me in the middle of the highway (which I try to avoid because of the stuttering problem). With my luck getting worse, it now hestitating right before I take off.
Please can someone help me. I am desperate.

How bout the catalytic converter. When its gets plugged, it does some strange things to performance and acceleration.

How bout the catalytic converter. When its gets plugged, it does some strange things to performance and acceleration.
Thank you. Do you know how I can get that cleaned out? Is it something that I can do or do I need a professional to do it?
You are an angel for responding so quickly!

don't clean it out, unbolt it and replace it, you should be able to do it, but if you feel more comfortable have a muff shop do it. stock Cats are expensive, but will for sure fit. also the muff guy may charge a pretty penny as well, if they are dickheads. Now is the time to think about a catback exhaust though, since you need the cat anyway, might as well get some performance out of the car while it's there.

Hey lrbanda!!!!
Did you get the problem fixed? And what was it?

Hello, Ihave been having the same problem at first started at 30 and up. I replaced the o2 sensor. Now it does it between 43 an 58 mph. I unplugged the EGR valve vac line and taped off stutter went a way. New valves are between 35 and 50 buck to replace.

i had this happen it turned out the coil pack on the engine cracked and as it heated up water would get inside of it causing it to go all nutty at certain RPM,s