When I do a cold start, my IS makes a strange noise when accelerating, before the engine is warmed up. Almost sounds like a clicking noise, as if a leaf was in a belt or something, so everytime power is applied you hear the leaf hitting faster and faster. Like I said, once its warm, it goes away.

Tried looking on the forum and I can't find anything, beside a 2008 issue with water pump that users described being a similar noise.

Anyone have any insight?

 

Can you post some audio or a video?

 

Here is a video

 

Have a listen to this video and see if it sounds the same as yours. The vehicle in the video is a 2008, but the engine is the same as yours. Near the end he moves the camera near the battery and you can hear the sound a lot clearer.
If your IS sounds like his, then it's normal. The direct injection system and high pressure fuel pump are noisy...like a diesel pretty much.

 

Yep, pretty much the same sound! thank you

 

I have a 2104 IS 350 F-Sport, the sound is identical to this. Our cars are basically noisy, they do sound like a small diesel engine. There has been a lot written on this for other models: https://lexusenthusiast.com/2010/07/...engine-recall/

I thought it was a time bomb at first, but then realized that every Lexus I've been around sounds the same. Technically, the ticking is not indicative of a an engine "problem" but merely an audible result of the direct injection system...i.e., your injectors firing. Your fuel injectors have small electrical valves that open and close very quickly allowing a certain amount of fuel to be injected with the air your engine is drawing in. They sound like a sharp pencil rapidly tapping on a desk and be very rhythmic.

Complaints regarding this noise have been occurring for over a decade.

No biggie...drive with confidence.

 

Engines are particularly violent objects with a gajillion blunt metal parts and intricate pieces. It's amazing they're quiet as they are. But with direct injection, yes you'll hear a little bit more noise which is normal operation of the higher pressure fuel system at work. It's ok. Embrace it. Engine noise is cool and normal.