My 2000 deville is running rough when it's idling and when I'm at 65 mph the car seems to be jerking and have this awful smell, burning more gas and sometimes there's a little smoke coming out the tailpipe. It seems like the engine is revving with no power and when I go up a hill The car is straining and the transmission changes prematurely. Seems like the car wants to fly and it's not going anywhere and then it seems to clean itself out and run smooth but then he goes back to running rough.

check for a blown head gasket first https://www.youtube.com/watch?v=QA7KVQq9vKA