For about a month ago (the car is 2 month old) I start to have this annoying fluttering sound (sounds like a piece of paper stuck on fan) coming from the engine bay when I slowly accelerate from stop up to about 3-3500 rpm. Most noticeable when I drive on a smooth and quiet road. It doesn't matter when the car is cold or fully warmed up, I can hear it anyway. As soon as I stop accelerate the sound goes away. I've checked the intake and it looks normal, nothing loose. It's not the AC or cabin fan either as I have turned off the AC and still get this sound, but ONLY when I step on the gas pedal. The fluttering sound goes all way till the engine noise and road noise take over. And the sound is not there if I coast in same speed on same road.

Anyone have/had this problem?

Have booked a time with the service dept to check this out. The service guy mentioned that it could be the fuel pump and he said I should not worry about it. Should I really not to worry about this? The car is only 2 month old and got problem with the fuel pump already???

Can anyone educate me on this? I'm a noob

 

Well your doing what I would, take it back to the dealer and have them fix it. To me it sounds like it could be your fuel pump or even the air filter. Check the filter and see if anything is loose on the filter it self or loose in the holder as well. Just a thought, good luck very interested to hear what caused this sound.

 

Hey UpSideDown, Did you ever figure out what the fluttering sound was? It just started happening on my 2006 rx..... thanks

 

Can you record it and post the sound file or video? It could be many things, my first guess would be to check for exhaust leak.

 

I think it's the ACIS swirl butterflies. My 250 does this more on cold weather only. Once fully warmed up it goes away. The only thing I can think of is the nut is loose on the motor side.

You can check for play on the linkage. It will probably more loose on higher milage iS250's. I retightedned mine about 60k it didn't take much force to loosen the nut at all. Eventually it was probably going to back out.

https://www.clublexus.com/forums/is-...-solution.html

It may not be your problem. You can always ask your lexus service advisor too to check on it for linkage play.

https://www.clublexus.com/forums/is-...ank-1-a-2.html