fpt2001

I have a 1999 ES300 with 290,000 miles.

Until two weeks ago I was getting 26-28 MPG on the highway and the car ran great. Now it sounds like a 4-barrel carburetor opening up when I apply full throttle or accelerate to pass on the highway and the mileage is dropping quite a bit.

When I was younger and had my first car with a V8 and 4-barrel, we used to flip the air filter cover over so you could hear the carb open up under acceleration. This thing sounds exactly like that.

I have checked and there are no air leaks.

Any ideas?

PFB

Did you check for Exhaust leaks?

ES300NZ

clogged air filter ? I'm thinking you're describing a high level of intake velocity (air)

Chuckinnj

Check for a leaking flex connection on the exhaust....... Mine leaked whenever I hit a puddle of water.

fpt2001

Air filter, air intake hoses, exhaust, all tight. No leaks. This is less like air rushing by, it has a deeper internal sound. I am going to take all the air intake hoses off and thoroughly inspect this Saturday.

Chuckinnj

It is hard to spot the flex connector going bad........ Mine looked perfectly good even when I removed the Y pipe.

PFB

With the engine running, cover your exhaust pipe with the palm of your hand. Use a glove or similar as its hot.

Any exhaust system leaks will become evident.

If no leaks, the exhaust gases will be pressurized when you let go, or the engine may even stall

Phil