Mine made a rattling sound in that RPM range, it turned out to be something loose inside of one of the catalytic converters.

 

did you have to replace the cat or could you take them off and get whatever it was out? and were they stock or aftermarket?

 

I haven't examined them yet, only the passenger side cat was making noise. They were Kinetix HFC's.

 

^ It could be a broken weld creating vibration.

 

I get the car back in a week, the HFC's were removed so I'll be able to figure out what it was shortly.

 

I got an 06 coupe mt just about to hit 60k miles. Ive always used 93 octane or the highest i can get depending on location. i have the same problem its allways at low rpm in the first three gears just driving very chill. it sounds like it comes from right underneath the car. like it with be a metal plate/sheild/ bolt rattling underneath. I took it to my mechanic he listened around on the car with the stethiscope he said sometime is sounds like valve ping and other times it doesnt. But he said easy way to guess is run couple tanks with octane booster if it stops then its the valves. it never stopped.

you can pull the ebrake and let out a little on the clutch real quick giving it a little throttle and hear it. i plan to look further into it and ill post what i narrow it down to.

 

okay... so many people think you need higher than 91 octane gas. you dont. it will do nothing. there are so many threads on using octance higher than you are required to use and how useless it is.

the jist of it is that a higher octane gas can handle higher compression. since we only need 91 or 92 (whatever is available, where i live its 91), using anything that handles more compression is simply a waste. unless you have some type of forced induction haha.

All these guys talking about a loose heat shield - that sounds like a possible problem. Things can rattle at different speeds because once youre at a higher RPM the forces from your engine may kinda push things into place and keep things quiet. Or maybe you just dont notice when you hear that sweet exhaust note . My friend has a old cav and his engine mount keeps getting loose. it always rattles at low rpm. i would say this problem is due to SOMEHTING being loose. who knows what though haha. I really hope you guys find it. I'd say lift the car and just tighten stuff? there are so many possibilities its hard to tell... hopefully its not an engine or tranny problem!

 

i had rattling last year, turns out to be the loose heat shield. it was an easy fix but now its doing it again, so have to take it to the repairshop. Will update!

 

April fools!!!

 

^lol

 

It's just a trademark of any Infiniti vehicles. It could be any of the following.

exhaust heat shield
interior dash
loose bolts in the brace under the rear seats.
loose bolts in the sunroof rail

There are over 77 TSB's and it's best to just lived with it if you're out of warranty.

 

^^ Best answer so far ^^

Another fix is turn up the radio...

I can't expect my 05 coupe to be perfect anymore...it's just well driven...

 

well i think i found out the cause of my rattle and found a good clip of it too. it happens exactly like this guy's, but more metallic and usually louder and longer when dropping revs more slowly in gear rather than revving in neutral...
took it into a nissan/infiniti specialty garage (cin motorsports in charlotte, highly recommended) and the guy said it was one of the Berk HFC's. i was afraid of that since it never happened until a week or two after i put them on, but was hoping it was something else. he listened to it with a stethoscope and even took them off and heard something rattling around inside when he shook one.

kinda disappointing that Berk's cats would crap out so fast for no reason, and after searching specifically for "Berk HFC rattle" it sounds like a good number of people have had the same issue. i love their sound otherwise but am really turned off by this.