I noticed an annoying rattling noise coming from under the car, about 3 months ago, especially notable when pulling in my garage, only at RPM 9000-15000 at idle and while driving. The car showed no other symptoms, no loss of power, no warning lights, no hesitation, nothing, so I did not pay much attention, but it finally annoyed me enough that I took it to the dealer. The first time, they said they don't hear it, of course; then I had to go in and press gently on the gas, and they said, Oh, that could be anything but likely catalytic converter.

Yes, the nosie was from the passenger side catalytic converter, and unfortunately since I have 86,000 miles on the car, it would cost $1100 to change the CC. The CC is covered for 8 yrs/80,000 miles, whichever comes first.

California Emissions Warranty | Federal Emissions Warranty - SmogTips.com. Don't pay for replacing or fixing emissions related automotive parts which are covered under the California emission warranty or Federal emission warranty.

FYI, I always fill up with 91 octane gas and always use full synthetic oil, recently switched to Pennzoil Ultra x 2 DIY changes, never go over 5000 miles for oil/filter change, oil filter Wix and just cleaned TB's.

I just wanted to post this, so that if anyone owns their car and hears this rattling noise, make sure you take care of it before 80,000 miles, after which the CC will not be covered, and only the Infiniti dealer carries the CC for car models 2008-2009 and above-perhaps even 2007, according to multiple exhaust shops I called. I live in california, which apparently has the strictest EPA regulations.

 

I had one CC replaced at 50K miles. Anyway, look in the For Sale section. Usually you can find a pair of CCs for $200-$300.

 

Maybe it's time for an upgrade to some HFC!!!!

 

My cats were fine, however they had to replace my mufflers due to a rattle sound. My car sounds so much better now.

 

This happened to my driver side cat around 38k... internal rattle, apparently the honeycomb material broken loose and started moving around. Sounded like marbles in a can with light throttle load around 1100rpm. The dealer replaced with a brand new cat under the base warranty.

Now my passenger cat is doing the same thing, but my base warranty is gone due to age on the car. 42k right now on the car. Good quality cats right? I asked the dealer to diagnose and replace under powertrain or the federal emissions warranty.

No love... apparently to get the cat replaced under the 80k federal warranty, Infiniti/Nissan requires the car to be throwing a check engine light stating a cat failure code. They will not replace the cat just because of an internal rattle without a failure code. I even contacted Infiniti Customer Service and stated the issue I was having with the car and dealer not replacing. They gave me the same reason.

If anyone else has a different experience getting a cat replaced under the 80k without a code I would love to hear it!

 

idling at 15K? youwill hear noise alright......but only for a short time

 

Are you sure that's the right noise? I've had a similar noise and just figured out that it's something in the ventilation system right in front of my passenger seat. I only hear it at idle and goes away otherwise. Originally thought I had the same issue you described. Thought it was coming from near the inside air filter, but after checking that out found that it's in the vent pipes in the floor that go to the rear passenger side for heating. It sounds like a penny is in there when I tap on the top of it. Not exactly sure how I'm going to get all the way up in there to fish out whatever it is. FYI....I don't hear the noise from outside, so if you do just ignore this reply.

 

That low rpm rattling from underneath the car is the catalytic converter.

 

 

I had the same thing going on with my g that you are describi g. did not take me three months to find the culprit hate noise I can't explain on my g. mine turned out to be the heatshield around the cc rusted out.. check that get under your car and take a look don't go to dealer for that **** unless your under warranty.

on a side note anyone know if I can get that fixed under runt warranty?

 

Thank you so much for this info. I believe this to be the culprit. I will have to check it out and see if it truly is rusted out. I do have a warranty still, but not sure if this would be covered.

 

Same thing happened to me. Went to dealer and they did a diagnosis (300 dollars later) and they said my left cat is internally loose. They wanted 1100 to replace it and I said **** that. Dealer will rip you off no matter what. Seen people sell 2 of them for under 200 dollars and the dealer wants 1k for just one?! What I would/ what I am going to do is get HFC. You will prob end up saving money by doing that and having a performance shop install them. BTW I have an 09 G37x coupe

 

Really need to hear from anyone about either being covered or denied the 8yr/80k federal emissions warranty to replace a catalytic converter that has the broken honeycomb rattling noise without a failure code. My current situation above is while I'm sitting at 74k miles on my 13' G37xs coupe. The dealership is telling me they will not replace the cat unless the error code is thrown and the check engine light is on. Without just giving in immediately, what should I do? What can I do? Anyone with experience on this please help!

 

Hey!. I have a 13 G37x and I had NO CODES OR CEL but had mid body rattle so I did my due diligence in research and combed down the issue to my CAT. I went to the dealership I purchased my G from and said I have a mid body rattle occurring at low idle and/or low sped. I said I believe my CAT is bad/malfunctioned. Sure enough, they called me the next day and said they'd be ordering a new CAT (BANK 2) and they did. Issue resolved.
For your situation.... go to a new dealership, sounds like a bunch of people trying to make money off you.