it produces smoke from exhaust
by Visitor in Tarrytown, NY on June 28, 2010
If the RPM is fluctuating it could be from many different things. Something as simple as low coolant level, a vacuum leak at the intake manifold, or air induction. The idle control system could have a problem but the smoke coming out the exhaust, if it is steam due to a blown head gasket the smoke will be white (steam) and maybe smell sweet, if it is excess fuel the exhaust smoke will be black, if the engine is consuming oil the smoke will be gray. It is hard to say what is wrong with out being able to experience the problem first hand.