New to the forum, and my first Corvette too. But not new to car mechanics.
I have an occasionally recurring exhaust smoke. It seems to be an excessive rich smoke, not oil, not coolant. It is not slight! (good sized, pretty thick cloud). When it happens it lasts a few minutes or more, and when I drive it and the temp increases, that usually cures it, but not always. Also the idle is not as even as I think it ought to be, and sometimes there is a flat spot accelerating off idle.
Aside from those things the car runs very strong and smooth.
Recently completed work:
New MAF sensor, new ox sensor, new IAC, new plugs, rotor cap and wires, removed and cleaned TB, new radiator and fan (etc). Vacuum seems unbreached.
I have a few hunches, but I need experienced input. I am suspecting (roughly in order): EGR valve/switch, ECM, injectors, fuel pump, fuel pressure regulator, TPS. The car throws NO codes.
What could make this engine go from a sweetie pie to a smoky old hag (and then back) intermittently like this? Sometimes it goes days between episodes, sometimes it's twice a day. Or am I looking in the wrong arena? Maybe I have a sticky ring? The car had almost no miles put on it in the last few years. It has 100k total to date. It acts and drives very good other than the above.
TIA for any ideas. Real nice forum you have here.

 

Is this smoke only on startup when it's cold, or while driving?

 

I am thinking intake manifold leak if this is after the car has been started. If on start up its the valve seals.. One more thing that come to mind is, Maybe the oil is getting sucked up though the PVC valve and getting into the motor that way.

 

If, in fact, oil is getting sucked in through the PCV system, what can be done about it? I think my oil consumption problem is caused by that, but I do not know what I can do to fix/stop it.

 

It happens a few seconds to a few minutes after startup.
I just replaced the TPS and fuel pump. Damn this thing idles and runs nice now. I think that might have done it, but I will be on the lookout for an intake manifold leak along the way.
I examined the PCV situation and I doubt that it is sucking any oil, since it looks so clean. Also the smoke does not seem to be oil but very rich gas type smoke. I hope I have seen the last of it.
Thanks for the tips, very helpful. I'll be hanging around here. There's always lots to learn. My new hobby car is a 'keeper' that's for sure.