1994 4 runner smokes when started.

What colour is the smoke? The easiest way to check this is on first start when the engine is cold. This can give clues as to where the problem could be. is the vehicle doing anything else different?
A blue exhaust smoke is commonly oil getting into the cylinders. White smoke suggests coolant getting into the cylinders. Black smoke is the engine running too rich. Blue or white smoke can often mean a blown head gasket. On a 2001 engine that could the most likely reason.

Depends on where the smoke was coming from. I would bet it's oil smoke but it could be coming from a blown head gasket or it could be from an oil leak hitting your exhaust pipes. You likely seized the engine after it ran out of oil.

first step is to check and see if there is any oil left. If nothing shows on the dipstick, does the engine still turn over? If it does, pull you speak plugs one at a time and check them for oil or possibly coolant. If you have fouled plug(s) you blew a head gasket.

when you check the oil see if it looks like a chocolate shake. That indicates a blown gasket because coolant is mixed in.

either way you are likely looking at a big repair bill. You should have pulled over when it started smoking and definitely should have stopped when the lights came on.

If it is a 4.0 strait six cylinder this is a common problem on them.Mine was located just below the oil filter and is pretty easy to fix.Plan it on your next oil change and it is even easier to change out.Oh just so you know your 4.0 liter engines do make a little bit of noise but are pretty much bulletproof if you just do regular maintence on them.Next time you start it put your ear down by the driver side hood hinge.You will find some tapping noise there it is part of the evap system.If it had no oil pressure you would know it rite away.

Take a compression test on # 4. It may be a little oil burning w coolant getting by the head gasket. POSSIBLE faulty injector or not firing on time. Ck for any oil in the anti freeze or anti freeze in the oil.

Valve stem seals can cause this problem, but normally only when first started. Oil in the rocker cover seaps through the oil seals into the cylinders and is burnt up on start up.
Try a "STOP A LEAK" additive and it may reduce the oil consumption and smoke.
I found some on e-bay and it worked on my tired old escort. It even stopped the rattling tappets.

on the cylinder head ,u must check for the oil seals on for the valve if one of the oil seal leaks engine oil will come to the compression chamber,this oil burn and make that white smoke

Check to make sure the PCV Valve is working...when you remove it from valve cover and shake it...you should hear ball inside rattling, and even though it's running ok, you might need new piston oil rings and/or valve job. In the mean time you could try products for "stop oil burning", or change your oil to a heavier weight...if you're using 10w30/40 try 20w50 and see if that helps.

yes that has 4.0 liter and it hold 9 quarts with filter change use 20w50 thats what the factory calls for

Sounds like a warped head.

What car , and year and engine? What color smoke?