i have a 91 z-28 with 350 TPI. When you first start up the car it puffs alot of smoke? The car has alot of miles hard miles. 177,500 miles. But still runs strong. My problem is once it has been run for awhile it wants to rev up and down. When it is in park it revs up a few hundred rpms from a mormal idle than goes back to normal and keeps doing that. It like if the air was on. It does it at a idle going down the road to. When you first start the car it does not do this. Whats going on?

 

mine used to do that funky idle too....after the transformation it doesn't do it anymore...

as far as the smoke on start up, what color is the smoke? if its blue, your rings or valve seals are shot...if its white, your getting coolant into the combustion chamber one way or another...

 

im guessing your problems are coming from multiple places.

You are probably getting oil leaking into the cylinders which is causing the smokey start up, be ready for a rebuild.

The hunting at idle is often from the IAC valve (idle air control) which is located by the throttle body it just gets clogged up with carbon deposits and needs cleaning out.