Louder exhaust cold and P0420

[andrew_j]

My exhaust is louder cold engine only and seems normal once warmed up in a 2013 Acura RDX with 169k.

A P0420 check engine light went on coincidentally when this started happening, note it shuts off for few days and returns. Are they related?

I will add noise is front of vehicle around engine.

 

[JohnnyG]

A possible broken baffle in the muffler or broken catalyst in the converter.
How many miles on the vehicle?

 

[Furious]

You have an exhaust leak before or at an oxygen sensor.

P0420 means catalyst system efficiency below threshold, which would be the result of an exhaust leak.

Soapy water in a spray bottle is your friend with the vehicle safely on jack stands and the engine cold, additionally you could use a smoke machine or even a shop vac with soapy water as well.

 

[Nukeman7]

You are in the salt belt, so I'd start by checking for an exhaust leak at the mesh flex pipe between the manifold and the catalytic converter. Block off the tailpipe outlet with a thick rag while wearing leather gloves and look/listen for signs of exhaust leakage.

 

[slacktide_bitog]

If it's loud, that sounds like it could be an exhaust leak

 

[Rand]

likely the flex pipe at front.. if equipped.

 

[andrew_j]

I took to a local reputable old school exhaust place as friend who fixes typically has no ability to weld in his shop.

It needed a pipe , y pipe and flex and no bolts were holding those parts together before (northeast salt rot).

I presume P0420 will go away after a few drive cycles as it was leaking upstream of the latter 02 sensor.