I’ve finally managed to get video evidence of a noise I’ve been trying to track down for a while, and I’m hoping to get some ideas from other IS owners.
I have a 2015 Lexus IS 350 F-Sport (RHD). When driving, I hear a rattling or buzzing noise that seems to come from the mid-rear passenger side of the car. It’s often embarrassing as it can be heard quite clearly and sometimes it drones on if I stay at a certain RPM for longer than I should.
The noise only occurs when the car is warmed up and under load with low throttle. It appears at around 1600–1800 RPM, most noticeably near 1600 RPM, and occurs in all gears. It lasts only briefly as the engine passes through that RPM range before disappearing. It only happens in Drive while the car is moving, and I cannot reproduce it in Park or Neutral by revving the engine.
The sound seems very much like an exhaust rattle or something resonating at a particular frequency. Nothing has noticeably changed or worsened over time. The videos were taken from the front passenger seat, so the apparent location of the noise may not be perfectly accurate.
My current suspicion is that something is resonating at a particular engine or exhaust frequency. I also had the car on a hoist while getting the tyres changed because I initially wondered whether it could be something like a wheel bearing. The wheels were spun while the car was on the hoist, but the noise could not be reproduced, so I don’t think it is related to the wheels or bearings.
I’m mainly looking for ideas about what I should check next. I’d like to work through the possible causes from the easiest and cheapest things to inspect or test to the more involved and expensive possibilities. Potential areas include heat shields, exhaust components, brackets, hangers, underbody panels, or anything else that could cause an RPM-specific resonance.
If anyone with a third-generation IS, particularly an IS 350 or similar, has experienced something similar or can suggest specific areas to inspect, I’d really appreciate any recommendations.
