Stock exhaust sounds like an open exhaust

[A2andres]

17 SQ5 with 112,000

Recently had to replace passenger side cat and replaced it with an OEM style version from MagnaFlow.

It’s been installed for about a month with plenty of miles without issues.

Yesterday I noticed a distinct rattle sound coming from around the passenger side cat.

It got progressively worse/louder where now it sounds like my car is running a dump tube.

I popped the hood to check things out and the passenger side cat has a threaded bung that I can’t recall had a “plug” in it or not. If it did, it doesn’t anymore.

Either that or maybe the flex section between the cat and the downpipe is knackered.

Here’s pics of the bungIMG_2657.jpg
IMG_2656.jpg


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[A2andres]

Small update.

When I pop the hood and hold my hand over that open bung, there’s literally pulsating exhaust coming out from it.

I’m assuming there a bung plug that somehow worked its way out?


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[WolfsburgVW96]

Small update.

When I pop the hood and hold my hand over that open bung, there’s literally pulsating exhaust coming out from it.

I’m assuming there a bung plug that somehow worked its way out?


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Looks like your oxygen sensor backed itself out. It should look like the first picture you posted and you can kind of see the wiring at the bottom of the second photo from the looks of it.

[A2andres]

Just an update to close the loop. The magnaflow cat has an extra 02 bung that isn’t used and instead comes with a bung plug that somehow worked its way loose. I’m assuming my installer just didn’t tighten the plug enough.

These bung plugs are surprisingly hard to source but luckily I had the old downstream 02 sensor that I replaced when I had the cat replaced and just threaded that in there while I wait for the proper bung plug to arrive.

There - you can all rest easy now.


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