So we are new Lexus owners but we did purchase a older 2000 RX300 we absolutely love the car but we’re having some issues and don’t know what it could be! So it started out as check engine light throwing cylinders 2 and 4 misfire so we changed all plugs and after changing back plugs it started spitting white smoke from tail pipe and loss of power along with super low idle to the point of stalling out when starting the car also when you stop at stop light and go to take off no power please someone help we’ve already sank a lot into the mechanic and they can’t even figure the crap out! We thought it could be an O2 sensor but again we are at a loss!

 

White smoke could mean coolant is burning which could be a head gasket. It could also cause the misfires.

But please don't just start changing parts, including sensors, without better diagnosis. The plugs were probably fine.
If you wanted to test them you could easily have swapped #2 and #1 to see if the problem moved.

Are you still getting misfires or other codes?

 

Awww man that doesn't sound good at all and you just bought the car.

You got any pics or video of this smoke and when or what driving conditions it is smoking?

 

first off. do NOT drive the car any more. You can ruin the engine.

99% if white smoke is coming from the exhaust, you have a blown head gasket.

if the smoke is more "blue" that would be oil burning. If the white smoke smells sweet, that is coolant.

You need to drain all of the oil. Look at it and see if it looks "milky". If so, that means coolant. Which means blown head gasket.

You should also perform a compression test. That will help you see the shape of the engine. It will also help you determine the blown head gasket.

Again, do NOT drive or run the car any more. A blown head gasket is a serious issue.

 

I would like to hear more about this.
What does the smoke smell like- sweet, raw fuel, something else???

This concerns me, just saying... "we’ve already sank a lot into the mechanic and they can’t even figure the crap out!"