O2 sensors

[truekoa]

It's time for me to replace them, I've been getting bad mileage, rough idle, and I'm sure it has never been replaced before.

Does it matter which is downstream or upstream? Isn't it the same sensor?

I have one that I've purchased way back but never installed, how can I tell if its up or down stream?

It's an Ac delco unit part # 19178958.

Anything else I need to know in changing them?

Thanks everyone

[crazytrain65]

Re: O2 sensors

I would think they're the same, but i'm not sure. And when changing them be prepared for the passenger side being a B*tch to get unplugged and plugged back in, its way up in there. Make sure you use anti-seize too when putting on the new ones. Should probably spray some PB blaster or similar on them if they've been on there a long time.

[truekoa]

Re: O2 sensors

dumb question....theres 3 right?

one on each header and one near the cat?

[ssms5411]

Re: O2 sensors

Yes, there should be 3 on yours ,2 header O2's with small retangle plug ins, and the before CAT with a bigger square plug in. On 97 and below we have 4 O2's the extra one is after the CAT. I hear ya, I will be replacing mine here soon too, except they are Delphi's I think.

[truekoa]

Re: O2 sensors

hmmm

I understand that if you are running catless then you can get an O2 sim? However does that cat O2 sim actually affect mileage and performance?

I'd think its just the two on the headers?

[ssms5411]

Re: O2 sensors

Just the 2 headers(pretty sure since I have mine deleted), but if you want to tune for MPG then a wideband and Hptuners would be a great investment. I'm running 65lb injectors and got 24 MPG last tank city driving and getting on it alot, highway/city I have got 28 mph before watching my right foot.LOL

[pace2006]

Re: O2 sensors

hmmm

I understand that if you are running catless then you can get an O2 sim? However does that cat O2 sim actually affect mileage and performance?

I'd think its just the two on the headers?

The O2 sensor by the cat has no other function than to tell you if the cat is functioning properly or not. It doesn't affect the car's mixture or performance (unless the cat is clogged or deleted and not tuned out).

[enzia35]

Re: O2 sensors

I used Delphi's. Slightly cheaper from rockauto, and they seem higher quality.

[firebird19_99]

Re: O2 sensors

not to steal your thread i just wanted to know how many 02 sensors 99+ cars had. wat exactly is an o2 simulator, which 02 sensor does it substitute for and is it hard to install?oh which one is a good one? im redoing my whole exhaust and wanted to know if i should just put an o2 sim in, thanks

[pace2006]

Re: O2 sensors

not to steal your thread i just wanted to know how many 02 sensors 99+ cars had. wat exactly is an o2 simulator, which 02 sensor does it substitute for and is it hard to install?oh which one is a good one? im redoing my whole exhaust and wanted to know if i should just put an o2 sim in, thanks

Your car has 3 O2 sensors. One on each exhaust manifold and one by the cat. An O2 simulator is something that can be wired in place of the downstream O2 sensor by the cat. Install depends on which one you get, some are plug and play.