O2 Sensors

[dave_from_Tennessee]

I have a '97 328i with around 140k miles. I passed my emissions inspection back in December just fine. I've heard that on my car the O2 sensors should be replaced every 100k miles. The car had 112k when I bought her, and I have no idea when they were last replaced. How many of them do I have, and should I go ahead and get them replaced this year? One more question, about how much should I expect to pay for this job?

[mcoupemindy]

Since it is a '97, you have four oxygen sensors. Two before the cat and two after the cat. It's a complete waste to change the ones after the cat IMO unless you get a check engine light. The O2 sensors for our cars are about $70 each and I expect if you take it to a shop, they will charge 1-2 hrs labor depending on the PITA it is to get them out.

[dave_from_Tennessee]

I believe those O2 sensors may be more than that. I just checked Bavarian Autosport, and for OEM they cost $112.95 each, that's $451.80 for parts alone.

[mcoupemindy]

I believe those O2 sensors may be more than that. I just checked Bavarian Autosport, and for OEM they cost $112.95 each, that's $451.80 for parts alone.

I stand corrected, I just looked at list price and you are right. Remember, you only really need two as the only purpose of the second two downstream is to ensure the cat is working properly. There's no need to change them unless you get a check engine light.