Catalytic Converter R/R

[donl]

About to replace catalytic converters on 2003 4.6L Expedition; will be installing a Magnaflo cat back system behind them as well. I am replacing the cats since I have read that they have typical service life of 150K miles and I have 125K on the clock. Since I will be under the vehicle anyway, I am thinking why not replace the cats now. No obvious signs of clogging but fuel economy has slipped a bit in the last few months. One of the forum sponsors has recommended the Magnaflo cats to replace the OEM cats, so that is the hardware I will be using.

No issues with the cat back install and the R/R of the cats looks pretty straight forward. However, not having done this before am curious about the O2 sensors.

1. Is a special socket required to remove the O2 sensors? If so, where do I get it?
2. Should I replace the O2 sensors? If so, with what? OEM or aftermarket.

 

[FordandPolaris]

Yes they do make a special O2 sensor socket. Check with a local Autozone or O'Reilly, they should carry a kit that you can rent for free (pay a fee up front, get reimbursed in full when you return the kit). I would replace the O2 sensors if you are concerned with fuel economy. I have tried to get mine out, but they are rusted in place. Hopefully since you live in a dry area of the country, they will come out easier for you.

As to what to use, I don't think it really matters, I was going to use the cheapest ones O'Reilly carried when I was going to do mine. Not sure of the laws in Texas, but if you don't have emissions in texas, only replace the upstream ones. They are the only ones that affect air/fuel mixture, etc. If you do have emissions testing, replace all 4.

 

[donl]

Yes they do make a special O2 sensor socket. Check with a local Autozone or O'Reilly, they should carry a kit that you can rent for free (pay a fee up front, get reimbursed in full when you return the kit). I would replace the O2 sensors if you are concerned with fuel economy. I have tried to get mine out, but they are rusted in place. Hopefully since you live in a dry area of the country, they will come out easier for you.

As to what to use, I don't think it really matters, I was going to use the cheapest ones O'Reilly carried when I was going to do mine. Not sure of the laws in Texas, but if you don't have emissions in texas, only replace the upstream ones. They are the only ones that affect air/fuel mixture, etc. If you do have emissions testing, replace all 4.

Thanks. No emission testing in Texas. By "upstream" I assume you are referring to the sensors closest to the exhaust manifold? Yeh, drier here for sure but if I can't get the existing sensors out, I will just have to replace all four.

 

[FordandPolaris]

Thanks. No emission testing in Texas. By "upstream" I assume you are referring to the sensors closest to the exhaust manifold? Yeh, drier here for sure but if I can't get the existing sensors out, I will just have to replace all four.

Correct, the ones that are after the catalytic converters (downstream) only detect if there has been a change in the exhaust from the upstream sensors, thereby signalling the cats are working to a certain extent. If they do not detect enough change, it throws a code and turns on the CEL, but does not change the running of the vehicle like the upstream ones do.