silenc3x

I'm hearing this rattle noise towards back of car sometimes around 1500 rpm as the RPM are dropping. You can hear it at 7 seconds in the video below.

Seems to be in the back of car, in front of rear axle. Maybe cat related rattle? I do have an EVS tuning high flow cat and UK mod.
What do you guys think? Also, there aren't any CELs or other issues that would help diagnose.

nubbel

Broken cat

Broken catalytic converter substrate isn't going to damage your car.

There is however a chance that the loose substrate might slide around and decapitate your O2 sensor (which can be pretty pricey).


(Image stolen from https://www.s2ki.com/forums/s2000-ta.../#post12218468)

On a second thought, if you are lucky the rattling might just be a loose heatshield around the cat

silenc3x

Well the HFC is only 3 or 4 months old. Maybe it was a defective unit. I should give it a smack to see if I can hear it rattling around. I don't think o2 sensor can be decapitated due to the design. but I assume it's not really doing it's job anymore if it's banging around...

I'll contact Evasive and if this is common.

Soviet

That sounds like a broken catalytic converter to me... or at least the sound of a catalytic converter rattling.

Sorta strange in your case since you have an HFC...

Say Chi Sin Lo

Hi all, I'm trying to figure out a rattle sound as well. It's intermittent at best.

Can the catalytic converter rattle be heard from inside the cabin? More importantly, does it "shudder" upon shutting off the car?

I'm trying to figure it out. My 2nd guess is dead motor mounts, but visual inspection does not yield any brown/orange fluids around the mounts.

Soviet

The catalytic converter rattle can certainly be heard from inside the cabin but it is a more intermittent rattle. I don't think it shudders specifically when turning off the car.

There is a pretty good sound clip of a rattling catalytic converter in this video:
It is very loud

Say Chi Sin Lo

Hmm ok, I only hear the "shudders" when I turn the motor off. I guess that's good that I can kind of rule out the cat and focus on the motor mounts (I had planned on replacing them anyways).

Thanks!

silenc3x

It happens so sporadically, like I will notice it maybe once every week or two at most. It's not common which is weird.
I can start the car, get out and stand there until it warms up and wont hear it. Then randomly I'll hear it when I'm parking in my garage after a 30 minute drive. I've only ever noticed it when parking in the garage after a drive, as the revs fall. And it never rattles at idle. Very odd. Like maybe the core is partially cracked and only rattles in certain conditions.

Might just leave it alone and see if it gets worse. I still have my OEM cat if necessary.
Next time I'm at Honda for a service, I can have them try to replicate it to diagnose it. Theyll do it for free.

wakathi

It could be the heat shield. Has the bottom of the car scrapped any speed-bumps some time in the past? If so, the heat shield might have moved.

silenc3x

I don't have the heat shield is on it. That's still attached to my stock cat. I should still check for anything loose down there though.... and make sure those spring bolts are tightened correctly.