My car started smoking when I let it idle for about five minutes and burned oil too. It did not smoke on first start up in the morning. It did not smoke or burn oil when I was driving.
I thought that could either bad valve stem seals or broken piston rings.
So I decided to replace the seals since they are cheap.
When I took the old ones out, I noticed that the ones located on the exhaust valves had no upper ring.
I put the new ones in, and the problem disappeared. I don't know what could have caused the seals to lose the rings, I'm hoping that was the fact that they were a very low quality kind and that they went bad one time that my car over heated due to a fan solenoid malfunction.
Anyway, I drove the car 300 miles after the valve stem seal replacement, and have been driving it to work for a week, and it is working like a champ now, without any smoke when I let it idle, nor any oil consumption. Write that one down.
BTW That was the Trans Am