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Rattling noise possibly from Catalytic Converter?

(2001 Honda Accord)
in Potwin, KS on January 11, 2014
I'm a newbie here and really don't know much about cars or car problems. I have a guy I work with that has been trying to help me fix my car, but I'm not sure we've done the right things. I have a little communication problem with him as he doesn't speak a lot of English. My Check Engine Light came on a few weeks ago. He replaced all my plugs & wires and a sensor (?? Don't know which one). Then the light came on again a day later. I took the car to Auto Zone and they said the code was P0420 & P0430. I ended up replacing both the Front & Back O2 Sensors, but they said it could also be my Catalytic Converter. The light went off. Then a few days later I started hearing a rattling noise, and the guy that has been doing the work on it says it may be the Catalytic Converter. It is worse when you are idling and in low gear, low speeds. Seems to go away when at higher speeds. He says he knows someone that can "fix it" cheaper than putting a new one in. Does this sound reasonable? Can they be fixed or is it better just to get a new one? And if so does it make a huge difference which brand or does it have to be from the Dealer? The car has about 130,000 miles on it. 4 Cylinder - 5 speed. Any advise is much appreciated. Thanks! - Clueless in Austin :(
Displaying 5 answers & 1 comments
Popular Answer
on January 11, 2014
Take your car to a muffler shop and have it checked out! All that is needed here is to hoist the car, hit the converter with a rubber mallet to see/hear if that is what is rattling!!! If it needs to be replaced, see answer 2!! Most muffler shops have cat conv in stock.
on July 25, 2014
I'm not a mechanic but have driven Accords only since 1984. Your info helped me so hopefully mine helps you. That rattling sounds similar to how mine did. Mechanic explained the inside of the cat conv had crystallized & it sounded like small rocks in a shaking can so replaced cat converter with rebuilt one and was fine till I changed muffler. Not sure my mech changed sensors, so....
of G. T. Service Center on January 11, 2014
You don't have to get dealer cat's, others will do fine, all they have to do is work.
of Gillespie's Auto Service on January 11, 2014
The correct repair for a P0420 is usually to replace the catalyst. About the only things that need to be confirmed before doing that is to make sure that the O2 sensors are working correctly, (already done) there are no exhaust leaks, and that there are no software updates.

If the catalyst has broken apart it can rattle especially if you are tapping on the exhaust but you usually cannot hear it with just the engine running, that information suggests that its more likely that a heat shield is loose. Heat shields are actually important to keep the heat in the exhaust system and help the catalysts be as efficient as they can be.

If it is proven that you do need to replace a catalyst, you really need to go with an O.E. (original equipment aka dealer) or at the very least a CARB certified OBDII catalyst. (California Air Resources Board). In the past when there were no restrictions a lot of catalysts that were replaced had the check engine light coming back on within six months to a year simply because they were too small to pass the computers onboard test. That doesn't mean they don't work, they just don't work good enough to pass the O.E. test because they cannot store enough O2 simply because they are too small. Because of that, states that are aligned with the California laws today all cannot legally install just any OBDII catalyst they must use the correct part. Basically if the parts book says "Not legal for sale in California" then you don't want it on your car.
on January 11, 2014
Hi. I am a car guy, I have many cars. I am not a mechanic, but have light mechanical ability. I usually hit analysis on the mark, I do problem solving for a living. First. I always suggest finding an independent garage, that you feel comfortable doing business with. The reason is that this mechanic will get to know your car and hit the repair on the mark. This eliminates guess work, repairing parts that do not need to be repaired. It will save you time and money in the long run. This sound can be from another source, not the converter and it may be reverberating from your differential, especially if it is happening at different RPM's. Take your car to a pro and pay for an analysis. Its a little money now and not a lot later. Also, buy a after market warranty that the garage you choose uses. After your deductible, everything is covered! Otherwise, go to a junk yard and buy another coverer, take it to a muffler shop and have them put it on. Good Luck.
on May 13, 2014
Hello, I have a question. I have a 2001 Honda Accord V6. I thought my engine was pinging so I took it to the dealer (it also needed it's 180,000 work). The next day I still hear this pinging noise so I took it back to the dealer and they narrowed it down to either from the single exhaust pipe or the 2 pipes that split to the mufflers. They put it on the hoist, but could only narrow it down to these pipes. Do you know what it might be? It was only doing it around 30-40 miles but now it's at any speed. Should I take it back to the dealer or what type of mechanic would you recommend? Thank you.
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