Subject: grey smoke and high rpm
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!