02 sensor replacement

Hey all gurus,
I have a rookie question about where are these o2 sensors located? After an oil change the other day the mechanic said I have a bit of a rough idle, which I have noticed. He then recommended the 02 sensors replaced, but at $99 each, I told him I'd wait. The parts are about $20 each on ebay, and they look to just be plug and run parts. I know there are the up stream and downstream versions, but where the hell is the stream. lol. Also should all 4 be replaced, my 5.3 engine has about 165,000 but runs like a champ. Any body replace these things?

Upstream is before the cat (i.e. between exhaust manifold and cat) Downstream is after the cat (between cat and muffler). The downstream cats do not affect preformance and are only used to monitor cat performance. Therefore, the upstream 02s should only be replaced.

Do they need to be replaced? It depends. A dirty throttle body can cause a rough idle as well as a leaking fuel pressure regulator? With 165K, it could not hurt to replace them.

//2000CAYukon

Just a quick question to piggy back on arix's post and what 2000CAYukon said.... Would it be benifical from the preventitive maintenance point to replace them anyway if you have over 100k miles? My truck runs good but does have a slight ping when I step on it and the throttle is at just the right spot.

Mine threw an ses light, and when I hooked up the palm to it, it told me it had a bad 02 sensor. The truck started idling rough and my air/fuel gauge started acting crazy as hell(the one pigtailed into the driver side sensor). Until it threw the light, everything was running perfect, so I wouldn't change them until I threw a light telling me too. Mine had 146,000 on it before it went bad.

If it doesn't throw a light there is probably nothing wrong with them. Most times an O2 sensor code is caused by something else upstream. it does not matter how many miles you have unless you like wasting money you gain nothing by just swapping them out.

ok, I was just wondering if an O2 sensor was something to do for preventative maint. Like changing a belt thats getting cracked. As for wasting $$, I'd rather spend $20 now than break down later.... but I'll save my money instead.

I would look into getting a throttle body cleaning (generally from the dealer), it did wonders on my '01 with only 80k miles.

i would buy O2 simulators and gut the converters hahaha

i would buy O2 simulators and gut the converters hahaha

I got the rear cut off in the tuning and just cut off the converters. :grinyes: The front has to stay on though. :wink:

Thanx for all the suggestions guys,
Well today I noticed that there is a loud whining noise coming from the gas tank. I'm thinking the rough idle could in part be attributed to my fuel pump being on the verge. It sounds like it is straining, but dies down once I get going. I know from my last truck it is a pain in the @$$ to replace. We'll see how long it lasts.

Thanx

The fuel pump on my 2000 5.3 has been loud for the past 50,000 miles, though sometimes the sound goes away. I've been telling myself that it's due to the placement of the pump - maybe against something that transmits sound. I'll go with that until the pump quits.