Q: My catalytic converter is rattling and there is smoke coming from my car. Is the catalytic converter faulty?

asked by on October 19, 2016

My catalytic had rattling for some time. I just never looked into it(BAD IDEA). Then 3 weeks ago I started my car, and it was idling so BAD. as if no air or pressure was being released through the muffler. I took it around the block and the car wouldn't even accelerate! NO back pressure. Then after I stopped the car SMOKE started coming out from the bottom. NOT from the engine or anything close to it. I took it to my mechanic for troubleshooting. I thought it might have been an ignition problem or battery etc.. he found nothing wrong with the coils or spark plugs or battery or anything! Heck he even checked the timing chain! the device just kept saying "RANDOM MISFIRE". NOTHING specific. Then i mentioned about the smoke and cats so he said that might be the problem. HE advised to take it to a cats/muffler shop. Before i go, i need a second opinion. It would be of great help if someone gave me a good explanation of what the problem might be. Thanks guys.

Kind regards, Kevin

My car has 150000 miles.
My car has a manual transmission.

It is possible the catalytic converter got hot enough to fail on the last trip you took before this started. No pressure from the exhaust is a good sign that the car can’t breath. This may be because it cannot get enough air or because it cannot exhale.

The only way to confirm definitively is to perform all of the tests the previous mechanic performed to confirm the diagnosis. There are a few other sensors that may cause similar issues, but the scan for diagnostic troubleshooting codes would have alerted you at that point. A muffler shop will be able to confirm if the cat is bad. You can knock on it and see if you hear a rattle of some sort. This is a sign the filter inside has become heated, brittle, and broken off on the inside.

I recommend having a certified mechanic, such as one from YourMechanic, come to you to determine if the catalytic converter needs to be replaced and why smoke is coming from the car.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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