Dead Catalytic Converter: Replace or Drive?

[Djvan]

Hello. I just went into a shop to gets check engine light read. Turns out one of my catalytic converters is "below threshold". I drive a 2005 Mercury Sable with 145k miles. Evidently the car has two converters, and the other is still operational - according to the mechanic. A few questions:

1) If the other converter is working, why did my check engine light come on. I assume it's an O2 sensor, post dead cat that triggered it. However, am I likely emitting the crap, or is the second car making up for it? Suppose the only way to know is by an emissions test?

2) I live in Philadelphia and only drives car once a week, about 4 miles. Grocery store and back. What long term effects will driving in this condition have on the car?

3) what's the cheapest way to get this replaced? My car is free and clear, but only valued at about $3000. I'd like to hang on to it, but if this is too expensive of a fix, I'm thinking Zipcar is my new solution..

Thanks for any help!

 

[Jimzz]

Swap the o2 sensors from the left to right. If you still get the same code then yea its most likely the Cat. If the code moves to the other side then its the o2 sensor. Many people read a code and go straight to a bad Cat when its the sensor.

The reason the code came on is the rear o2 sensor got a bad reading. This usually happen due to either a bad Cat not doing its job or a bad sensor sending the wrong information.

Check out eBay, www.rockauto.com, and amazon. I got a new Cat for my BiLs car very cheap compared to most places at eBay. Same if its just the o2 sensor.

 

[JulesMaximus]

Swap the o2 sensors from the left to right. If you still get the same code then yea its most likely the Cat. If the code moves to the other side then its the o2 sensor. Many people read a code and go straight to a bad Cat when its the sensor.

The reason the code came on is the rear o2 sensor got a bad reading. This usually happen due to either a bad Cat not doing its job or a bad sensor sending the wrong information.

Check out eBay, www.rockauto.com, and amazon. I got a new Cat for my BiLs car very cheap compared to most places at eBay. Same if its just the o2 sensor.

Agreed. I had a check engine light on an older car I owned a while back and it was one of the O2 sensors, I replaced it and never had another problem with the car after that.

 

[Djvan]

Thanks for the quick replies. As I'm no mechanic, could you tell me how difficult it would be to switch the O2 sensors? About how much labor is involved/what should I be paying someone to do this for me?

Also, after a quick search online, I found a broad selection of different catalytic converters, all of which claim they're compatible with a 2005 mercury Sable. The parts look completely different though; is there enough room under the hood for either or? What's with the huge price difference; $66-$700?

http://www.autopartswarehouse.com/search/?Ntt=catalytic+converter&searchType=global&N=0&submit=
O2 Sensors are quite cheap, about $40. Hoping for that

Thanks again!

 

[Hartle4]

Below threshold could be 5% less than what the computer thinks it should be performing at. The second 02 sensors on these cars only monitor how clean out going air is from the exhaust, if it was me i would just drive it, but the engine light wont drive me insane like it does most people. Make the light go off by putting a spark plug non fouler in the o2 sensor port and then screwing the o2 sensor into the non fouler. This will take the sensor out of the exhaust stream a little bit and keep the light off if it bothers you. Or you can spend the money to put a good cat on, the cheap cats will make the light come back on in a short time more than likely. I am a mechanic too by the way, it is what i do for a living.

 

[yhelothar]

I replaced the O2 sensor on my miata recently. It was a 20 minute job given it was a bit cramped there and I had to pull off the air filter box. But it's just one 22mm bolt for mine which I was able to get off with an adjustable crescent wrench and a cheater bar(pipe).
The O2 sensor is located right below the exhaust header and you'll see where the wire goes to. I was also lucky amazon carried a direct replacement for $32. It's very possible that you might not find a direct replacement and you'd need to splice the wires.

 

[jlee]

Thanks for the quick replies. As I'm no mechanic, could you tell me how difficult it would be to switch the O2 sensors?

If your car lives in the rust belt? Could be almost impossible. If your car lives somewhere nice (like Arizona ), it should be super easy.

 

[thedarkwolf]

Below threshold could be 5% less than what the computer thinks it should be performing at. The second 02 sensors on these cars only monitor how clean out going air is from the exhaust, if it was me i would just drive it, but the engine light wont drive me insane like it does most people. Make the light go off by putting a spark plug non fouler in the o2 sensor port and then screwing the o2 sensor into the non fouler. This will take the sensor out of the exhaust stream a little bit and keep the light off if it bothers you. Or you can spend the money to put a good cat on, the cheap cats will make the light come back on in a short time more than likely. I am a mechanic too by the way, it is what i do for a living.

Yeah I had an 03 pontiac vibe with 200k miles on it that would throw that code every couple months. I'd just clear it and ignore it. The computer throws the code if the cat drops below what 90% I think so meh 89% is still pretty good lol. I was going to do the spark plug non fouler trick if the code started coming up more often but I ended up selling it first.