When my 2006 suzki xl7 has been sitting for more than 3 hrs it blows bluish/white smoke in one big poof! what can this be?

If the smoke is a bluish white you have worn valve seals.

Is the smoke white, blue, or black?

Hello There

White smoke when first started is normal. If white smoke continues you have an internal coolant leak, i.e., cracked head/blown head gasket.
Black smoke is caused by a rich fuel condition.
Blue smoke is caused by oil consumption.

You need to check your oil cap for yellow/white gunk on the cap if you have this then this is a sign your head gasket is cracked. Check to see if your radiator coolant level is down this is also another sign.

Hope this helps. Please don't forget to rate me.

Many Thanks

Sell it quick then before it blows up or fails the vehicle inspection .

Thats oil caused by "blow by" it means your piston rings are wearing out or you have scratches in the cylinder walls, causing oil to "blow by" the rings and burn during spark. Only way to permanantly fix is to rebuild. You may get temp fix by using a product called restore. It is sold at autoparts stores.

when sitting condensation builds up and burns off when started its no big deal unless theres a lot of water in gas or oil put some seafoam or some kind of fuel stabilizer in it

whit smoke usually means youre burning oil. make sure that it is solid white smoke and it does not have a slight bluish tint...thats an entirely different problem

White smoke on startup could be a head gasket leak between the water jacket and the cylinder. Won't always show in the oil. Antifreeze makes it smell oily or sweet. Compression test will tell for sure. Bluish is oil that was burned. White is usually water or oil into exhaust after combustion.

Is it gray, bluish gray, or white? White smoke, during warm weather, indicates that you have a head gasket out and it's vaporizing water, it will look much like it does when you first start it on a cold day. Bluish gray indicates burning oil, which could be bad valve seating, severe engine wear on your piston rings and oil is blowing past them into the combustion chamber. Grey smoke is probably water as well, though it could be contaminated with oil, or the vehicle could be running too rich, getting too much gasoline. But typically this is more of a black smoke than gray.

This is not good. White smoke is usually coolant, but the deposits on the plugs indicates oil related issue. Major exploritory surgery is in your future.

Start with a leak down test, and based on the results of that, your next step will be more clear.

Sorry for the bad news, but you already knew that, with the smoke report.

I have a 1989 chevy silverado. my dad bought it new and never drove it. he wanted to pay it off first. after 5 years it had 15K miles on it. it then smoked everytime he cranked it after it had sit a while. The lack of driving it caused the rubber valve seals to dry rot. so now when it sits, oil seeps down between the valve and the seal and enters the piston chamber. when he cranks it, a poof of blue smoke blows out the exhaust but quickly disappears after the the initial poof of smoke.
this may be your problem also if you have abnormally low milage on the vehicle