Emissions FAIL; O2 and catalytic converter replacement

[westslope]

Went to the closest Air Care testing facility here in southern British Columbia the other day and failed. (The lower Fraser Valley boxes up bad air on occasion just like Phoenix, AZ or Greater LA.)

 

Went to my new mechanic in South Surrey: CJ's automative repair. They replaced the 02 sensor; was insufficient, and then replaced the catalytic converter with a new Walker unit. The mechanic had some difficulty with rust. Total cost ~C$850.

 

Returned to Air Care and passed with flying colours. The readings are better than they have been in several years.

 

Question: I gather that the O2 sensor is designed to last 60,000 miles or ~100,000km. Ours was switched out at 220,000km.

 

Should a person ideally switch out the 02 sensor at 100,000km as a preventative measure or simply wait until the unit fails?

[adamzan]

If it were me I would wait till it fails.

 

Mine is kinda messed up right now (makes the truck accelerate funny) but I still get good mileage. I have 275,000kms. I pass emissions here in ontario with flying colours. I had the cat replaced last summer with (probably) the same walker unit you have. My originals were plugged.

 

I have heard that if you drive with a bad o2 for too long it can mess up the Cat...

[Kingman]

Driving with a very rich fuel mixture will ruin a cat fairly quicky. I had a temp sensor go out on my rig, and it was dumping gas into the engine at incredible rates (half a tank in 8 miles). The cat was so plugged it would barely run and drive. So I upgraded to a Magnaflow high flow cat.

 

I don't see a point in replacing the sensor at intervals until it starts giving you problems. Running rough, poor power, and poor fuel economy.

[westslope]

Thanks gentlemen. The truck runs fine, seems to idle at slightly slower rpms.

 

Will check the fuel efficiency once I go through another tank or two. Have reduced highway speeds by 5 to 15km/hr in early 2008 and have decided to keep driving the slower speeds (typically 95km to just under 100km/hr. Driving slower increases fuel efficiency substantially.