2004 Chevy Impala overheating /stuttering

A 4 wheel drive impala?

Anyways the 3.4 motors are common for intake gasket leaks. Pull off your oil filler cap, is it yellowish inside?

What are the conditions AND levels of both the coolant and antifreeze?

LOL.I meant condition of oil and coolant. This should be an interesting post between the two of us. :D

IF you let it run at idle, does the cooling fan come on before it gets to the red zone on the gauge. Don't let it get there, if it gets to the border or it.

It sure could, that would have been my next direction. If I remember right there is a pipe right there that make it a little funner to change.

No, I doubt it would be a headgasket issue. Before putting that new stat in boil some water and have a accurate thermometer (and the new stat as weel as the old stat in the water) to watch the temp.

You want to see at what temperature these things are opening up at. They both should open at 195 degrees I beilieve. Should say on the new box of the stat. It the new one does, pull it out of the water and start installing it. Watch the old one and hope it doesn't open until a much higher temp.