Ok I have a 98 3.1. Earlier today it started making a loud knocking/chattering noise while I was driving at about 45 mph. I pulled over and topped off the antifreeze and added 5 quarts (!) of oil. When I restarted the car it kept making the same noise.

The weird thing is that the car won't accelerate right, it's VERY sluggish. and the noise level and tempo of the knocking coincides with the RPM. For instance when I start from a complete stop the knocking gets very loud and fast and I accelerate at about a third (or less) the speed that the car did before.

The car isn't overheating and I don't smell any burning, but then again I haven't driven it for more than 10 miles since the noise began.

Any ideas? Timing chain/belt? Cylinder? Gasket? I don't know enough about car engines to make an educated guess so any help would be appreciated.

5 qts?!, and now the engine is knocking, I would say it damaged the bearings and crank, don't drive it anymore, have a mechanic listen to it, sounds like the engine is damaged for sure!

I agree with Maxwedge, it sounds like you blew it up.