Hesitation shifting between 3rd and 4th

Ok, I got a 2001 Grand Am SE, 2.4 L engine. The car only has 42,000 miles on it. My problem is this-- when I am driving down the street and I hit about 42-45 mph the car starts to shudder like it isn't shifting into 4th gear(it's an automatic). I thought maybe it was a plugged fuel filter so I changed that, I also pulled the plugs to check them and figured I might as well replace them while I had them out. Niether of the changes helped. The reason I changed the plugs and fuel filter is because my wife went and put some cheap gas in it. I have tried running 93 octane gas in it to possibly clean out the system, but that isn't helping either. I am on the third tank-full of 93 octane gas(BP gas). Could it be the transmissing fluid and filter need changed? Or possibly the cat converter? I'm really in a bind and need some help.

maybe coil packs, or could be a clogged cat converter

If your vehicle has a MAF (Mass Air Flow) sensor, clean it first and test the vehicle.

I am having the same problem with the same car at 58k. I also notice it on the highway at 60 mph trying to accellerate and having the car hesitate.

I'm having the exact same problem. Girlfriend drove my car with sandals on, and she said it felt like the gas petal was sticky just a little bit. I put WD40 on the petal arm, and it stuttered less, but came back. Everyone else that drives my car says nothings wrong and they cant feel it... but i know it's there. How does one "unclog" their cat converter? or change the coil packs.... And, how would i know if i had MAF? i have a 2001 SE 2.4L with only 26k miles. Please AIM me or [email protected]

change your air filter and see if the problem goes away mine did....its a $6 fix.