ok i just replaced the alternator on my 94 grand am and now as soon as i take it out for the test drive it idles extremely rough and has a hard time just running at all if i am not putting my foot on the gas(like not all the cylinders are working). now when i take the belt off it sounds fine. there are very horrid rattling sounds coming from on of the pulleys. i believe it is the a/c cause i know that ive needed to replace it for a while now. also there seems to be white smoke coming out of my exhaust which signals a bad head gasket, but everytime i have changed my oil there is no signs of water in it. car only has 123k on it so i know it has plenty of life left in it. HELP ME!!!
GO EAGLES!

ok i just replaced the alternator on my 94 grand am and now as soon as i take it out for the test drive it idles extremely rough and has a hard time just running at all if i am not putting my foot on the gas(like not all the cylinders are working). now when i take the belt off it sounds fine. there are very horrid rattling sounds coming from on of the pulleys. i believe it is the a/c cause i know that ive needed to replace it for a while now. also there seems to be white smoke coming out of my exhaust which signals a bad head gasket, but everytime i have changed my oil there is no signs of water in it. car only has 123k on it so i know it has plenty of life left in it. HELP ME!!!
GO EAGLES!
the rattling noise might just be the pulley about to lock up on the compressor. and the white smoke is normal depends on how much . when its idle it usally smokes some when it kind of cold but if you could look out the window and see a cloud then your head gasket is blown or about to blow.

ok so my chiltons guide tells me i might kill myself if i try n fix it....so tomorrow when im fixing it lol. anyways to my point...im sure youve all heard of the fluids that are supposed to seal your head and all that jazz...normally i would automatically say no its all bs, but a friend of mine told me about this one brand in particular (tornado rings a bell) costs 60$ for one bottle and they gurantee itll work. just looking for some feedback on others results.

The rattling is likely your belt tensioner. The seize up after a while and by changing the belt, you may have loosened it a bit. Only problem is, once they are gone, they are gone. You should be able to hear it clacking while the car is idling. As far as the rough idle, make sure you didn't knock a vacuum line off when changing the alternator.

ok...so i was attempting to make it back ome with the rattling noise AND!!! tons of smoke pouring out of the exhaust...the damn car was struggling to do 40, it could barely make it out of first gear, and basically sounded like complete ass. i think whoever owned this car before me completely demolished this POS car. i mean it only has 123k. i know the head gasket 4 sure and possibly the water pump (fluid all over the belt and around the area the pump is) but god only knows what the hell else is wrong with this thing...anybody want it for parts lemme know...not asking much...new tires, alternator, belt, hoses, tranny is strong, headlights. whatever...thank god this is my back up car.