My 1996 sentra blowin smoke upon take off then goes away ,,runs quietly ..any thoughts...

It was just the residual oil or mineral spirit you used to clean the manifold.

Valve stem seals are leaking and/or valve guides are worn, opening the seals and allowing oil to run down valve stem. When de-accelerating, oil is sucked down the valve stems, then blown out when you start off. If it smokes under acceleration, then piston rings are worn.

The thick white smoke is either burnt oil or steam you can easily identify the smell of burnt oil not really sure why you thought it would be a good idea to put a 2 stroke mixed fuel in but more than likely that alone fouled your spark plugs. But if the problem preceded the fuel blunder then your either have a bad intake/head gasket, leaking valve seats, or bad main engine seal. Replace the spark plugs and check cylinder compression. Change your engine oil and check to see if it contains water/coolant also watch for coolant or oil consumption

The speed control of your fan has resisters that are in the venting system to blow air on them to keep them cool. If they overheat and or burn you will lose your low and medium speeds of the fan. If you run the fan at full see if the smell goes away. Your engine could be burning oil on the outside of the engine block, make sure that the weatherstrip where your hood meets the fresh air intake grill is sealing tight.

Depends on what kind of smoke. Sounds as you may have a small oil leak that is running down the engine and landing on the exhaust. When it drips on the hot exhaust it will smoke

Hi, I had the same problem, and is now fixed. Replace your idle control valve, and the idle problem will go away, and your car will be PERFECT!

you might check your valve seals if it does this moreso when its colder

common fault in this vehicle is air flow meter and temp sensor, if temp sensor fault normally will blow black smoke at the tail pie, air flow meter will have symptoms as you described.

Valve seals are leaking. If it does not use any oil I wouldn't worry about it.

Check the freeze plugs on the engine block.
These plugs/caps can leak when it is not sit perfectly.
Is the leak from tail pipe or from the engine area?
Start monitor for coolant and oil lose and report to the engine supplier.
Can you have a friend to do a drive along to see where the white smoke is coming from?

DO NOT rule out an incorrectly install head gasket set.