Mitsubishi Repair: grey smoke and high rpm, combustion chambers, coolant leak

Question
ok i have a 1991 mitshubishi eclipse automatic 4wd and about 4 months ago i
popped a tire and ive let it sat for a while now. now everytime i start the car up
the idle goes up to 2000 rpm's but what concerns me the most is that when i
push on the gas and accelerate grey smoke comes out the exhaust and is quite a
bit too. do u if thats and engine problem and if so what could it be and how
much would it be to go get it fixed

Answer
Abel,
Your car may just be burning off some of the carbon buildup in the combustion chambers and in the exhaust.  If the gray smoke has a "sweet" smell to it, that would indicate a coolant leak; possibly caused by a warped head gasket.  

If the smoke has a gasoline-like smell, then there is unburnt fuel in the exhaust.  This could be caused by a clogged air filter, bad spark plugs, or even a bad catalytic converter.

If the smoke has a burning/oil smell, that would indicate you are burning oil.  This could be what is happening.  Many times when you let your car sit for a while, the oil seals can dry out and shrink a bit.  This can cause oil to seep into the combustion chamber and burn off.

I would recommend doing an oil change with a new filter.  Drive your car around and if after a few hundred miles, if you're still seeing a lot of smoke, you may need to have your cylinder head rebuilt with all new valve seals, valve guides, and possibly even new piston rings.  If you need a head rebuild, that could cost over $1000 because it's quite labor intensive.  But try a new oil change first and don't make the decision to rebuild the head unless the oil change doesn't help.
Good luck!