Does anyone have one or two knocking sound coming from the back when you start steping on the gas lightly or when you stopping the car? My IS 350 is new, 3000 miles without any accident history. Recently noted the noise. Suspension seems to be fine without noise when going over bumps. It's annoying. I tried to crank up the Mark Levinson stereo but I just can't ignore it. I checked the the back seats, the trunk, and the spare tire compartment and I can't find anything suspicious that could have caused the noise. Anyone has similar problem or has any idea??

 

The mufflers on the IS tend to exhibit a lot of movement, moreso than other cars. When you initially step of the gas, the engine torque will shake the exhaust more-- it could be hitting something?

Hopefully the 2007 models use a stiffer compound for their exhaust hangar bushings.

That's all I can think of right now without actually hearing the car

 

I went to my Lexus dealer for the problem. They found the problem originated from a metal strap that wrap around the gas tank. They put a padding there and the problem resolved. My dealer's service department is great. They gave me RX330 as a free loaner car while my car is in service. They even washed my car. I didn't really want them to wash it because I am afraid they may scratch it. Lucky no scratch or swirl I can find so far. I still like to do the car wash myself to be safe.

Anyway, if someone has similar knocking noise from the back, pass on this message to them.

 

which dealership was this?

 

i've heard that noise, correct me if i am wrong but it is like a dull clicking not a high pitched sound. i have a system in the trunk and i thought it was that, but its great to know it might not be, can you give me some details on how the noise sounded, mine sounds like its coming from the trunk...mine also happens when i turn sharply, is this the same with you?

 

Let me describe the noise/sound a little more. The sound was one small knocking noise coming from the back. Only one knock each time and not continuous. It happened when I release the brake and step on the gas (even simply tap on the gas; not necessary stepping on the gas all the way). It almost happened everytime I do that. Sometimes also happened when I tap on the brake lightly or slowing down the car. Well make sure you turn off the stereo so you can hear it more clearly. If you have somebody drive the car and you sit in the back seat, you can hear it better. It's not from the suspension or the exhaust as there's no noise when going over bumps and there's as I shaked the exhaust and it's not loose. Not from the trunk as I removed the trunk net and everything else in the trunk and the noise is still there and when I seat in the back seat, I can hear it coming from underneath the trunk. I also checked the spare tire compartment and nothing is loose or rolling around there.

I took it to Pleasanton Lexus in California. The mechanic sat in the back and I drove the car to show him the noise. Of course he heard it too. It took them 4-5 hours to figure out where the noise came from. They checked the suspension and other structures. They finally found out the noise came from a metal strap wrapping the gas tank. ?The strap was flapping little bit?? They put a pad to cushion it and now it's fine.

I am sure my car is not the only one that makes that noise. I will recommend everyone who own 2nd gen IS to pay attention and see if it happens to your car also.

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IS 350, Metador Red, Black Leather, Lux package, Navigation, Mark Levinson system

 

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