1999 RX300 making bad noises under acceleration.
 

Hello! Over the last couple days I've ran into some weird noises under moderate to hard acelleration. When the car drops into 2nd gear, particularly at higher RPMs, it makes a sort of hissing/grinding noise.
Not quite sure what exactly is the matter, it started when I had to hard accelerate onto a highway, and I noticed the noise. Now it happens whenever, like I said before, accelerate moderate to hard.

Thanks for any help!
- Sam

Diagnosing over the net is going to a mostly miss, and a hands on examination is really what you need.

Is it just the noise or the vehicle is bogging down?

If it is just the noise, I would have the exhaust system looked at. The flex coupling has a tendency to develop a leak.

Salim

The vehicle seems to accelerate fine, I haven't noticed any lack of power aside from normal sluggishness when it's cold. I will look into the exhaust system, thank you for the tip!

Are you running 91 octane if not you might be pinging from low octane.
if you are running 91 your knock sensors might be getting tired mine are at 175,000 miles which I am going to replace.
I am going to also replace my timing belt plugs and all the rest of the stuff that goes with the belt.

I'd get it to a shop and have it test driven and inspected. Wouldn't just keep driving it and letting it happen. Might be causing more damage depending on what it is. A trick to get a free check is not to go to the counter and get talked into a diagnosis right away. Just play dumb and say, its making a noise, don't know what is it, just need to know if its serious or not. Then they'll have a tech drive it and give an opinion.

Let us know what it turned out to be