I have a 98 ES300 with 224K miles on it.
Lately I've noticed that when I drive and suddenly press the gas a bit more to pass a car for example, I hear a rattling sound from the engine. It sounds like metal hitting metal so I was thinking that it may be the valves. The sound does not come on when I drive normally. I also notice it when I go up hills as I have to give it more gas.

Does anyone know if these cars have to have the valves adjusted or are they self adjusting valves?

Can it be something else?

TIA

 

try a higher octane fuel...

what you're describing to me sounds like engine pinging or predetonation, or piston slap... whatever u wanna call it... all caused by bad ignition timing, or not enough octane...

 

That's a possibility.
I usually alternate on the low and high octane gas between fill ups but have not done so the last 2-3 months due to the high gas prices.
I will use hi octane next time I fill up and see if that works.

 

I agree with narfy. The low octane gas can save you a few bucks,but it the long run it will cost more money.

http://en.wikipedia.org/wiki/Engine_knocking