Pontiac Repair: car trouble

Question
I have a 1999 Grand AM V6 3400. I have white steam like smoke coming from the tail pipe that smell like burnt antifreeze, The collant light is on and off all the time, there is like a yellow grease lke water and oil mix on the oil cap and the pcv valve..the heat won't work most of the time it will heat up to about 230 then when it goes down to 205 the heat works for a min. then stops..it has a miss in it..we have changed the pcv and the eng.tempture sensor

Answer
Hi MAtt:

Well you have 1 of 2 things going on here. either a lowerinatke manifold hasket went bad and the coolant is leaking into the crank case and then the pcv valve is sucking the mixture in or you have a blown head gasket. More likely a head gasket due to the fact that it has an engine misfire. either way it's going to have to come aprat to see what the issue is. It may have had a intake leaking for a while and it ran low on coolant and overheated and took out a head gasket due to the over heating... what ever it may be do not drive the car because the coolant inot the oil will damage the engine bearings. get it fixed and have the engine oil chnaged a few tikmes to get the intermixed oil/coolant out. good luck :0