Oldsmobile/Buick Repair: ., blown head gasket, intake manifold gasket

Question
My 99 olds alero has two problems seemingly at the same time. It started running rough and had some white exhaust when it runs rough{this is off and on again} and smells terrible. It seems the thermostat went bad and I replaced it, but  the car is still overheating, this is also off and on again. Code checker said #1 cylinder misfire. Replaced plug and wire. Ran fine four about an hour and started same rough running. I am clueless on this one!

Answer
I would say you have a leaking intake manifold gasket, or a blown head gasket.

The bad smell is coolant burning in the cylinder. Same coolant fouls that plug.
If you pull that plug right after it starts missing, you will probably find coolant on it.
It will also be very clean.

Van