I have a 91 Camry 4cyl with a rebuilt engine that is about 2 years old now.

If the car has been sitting for five or more hours, when I start it, there is a small cloud/puff of smoke from the exhaust, white-gray in color, then no more smoking. I especially notice as I backup, wondering- "what's that cloud of smoke drifting by? Oh, its the car."

The car doesn't seem to be using any oil. My oil is still a nice clean brown in color, but it is getting close to time to change it. The puff has been going on for about a month now.

I have also noticed, occassionally, that at highway speed there is a faint knocking-type sound, like you get with bad gas. No drop in power or aything, so I assume that's what it is, bad gas. Otherwise, it runs like a top.

Anyone have any ideas?

 

What you describe is usually valve seals. There are rubber seals that help keep oil from running down the valve stems. When the car sits, and if the seals are worn, oil seeps down into the cylinder then burns on start-up. Not a serious problem but signs of wear. Long time idling can also produce smoke from this as well. The seals can be replaced with a fair amount of labor but on a 91 with one already rebuilt engine it might not be worth it. You should try to determine if the knocking is coming from inside the engine. Connecting rod or crankshaft bearing - that's potentially serious. Not all rebuilds are equal. Who did the rebuild and how much of a rebuild was done?

 

I have to agree with pedro and would not sweat it. I have a 93 that doesthe same thingbutusesno oil (225,000 miles). It has not detrimentaleffect and probably will not get worse.Just drive it.