My 1996 Buick Regal V6 was running great yesterday, and today it would not stay running when I started it cold. After warm-up, it would chug and die when I came to a stop. While highway driving, it would run very rough and seemed to strain when accelerating.
I detected a strong odor of gas and, when stopped, white smoke would come out of the exhaust. Also my power brakes do not seem to work while my car is missing and chugging. I have never had any problems with my car until now. Can you please give me some advice on what could possibly have gone wrong overnight?
Poor power brake operation indicates a significant loss of engine vacuum, which can be caused by a large vacuum leak, an internal engine failure, or something else causing a misfire in more than one cylinder.
White smoke coming out the exhaust may indicate a ruptured head gasket or cracked cylinder head. Either one will allow coolant to enter the combustion chamber and cause the engine to run badly. If that were the case, you would also notice an antifreeze smell along with the white smoke coming out the tailpipe.
The fuel smell can be part of the equation. The unwanted coolant will douse the engine's combustion process, allowing unburned gasoline to exit through the exhaust system. Get it to a good repair shop. They'll probably start by narrowing down which cylinders aren't firing, and take it from there. Why the big change overnight? That you may never know.