O2 sensor confusion

[sejinv]

Been reading this forum for awhile but this is my first post, hopefully I can finally get this sorted out with your guys help.

I know one of my o2 sensors has failed, but I cannot remember which one it was when I got the error codes checked. Now I was just going to replace them all, but I then remembered that my car has 2x before the cats and 2x after the cats. I have searched everywhere, read countless forums and manuals and nothing will give a definite answer, do I replace just the two before the cats, or all four, and if it is all four, are they the same part or are they different? I read somewhere that the two o2 sensors after the cats are only there to make sure the cats are working properly, but this information was vague at best. I am going absolutely insane trying to sort this out because I would like to just buy two o2 sensors instead of four.

I have a 1994 v6 Mustang, standard transmission. Mechanically it is stock, I have only made aestetic changes like rims, headlight/corner/foglight assembly.

Also which O2 sensors would you recommend, I was looking at Bosch, but I want to get the best ones possible with the hope that I wont have to do this again anytime soon.

Thank you for your help,

Sejin

 

[Lsredy2kstang]

Are you having a code or a MIL/Check engine light now?

Go get it read at Autozone or another parts place.

I would only change the one that is bad. They are expensive.

I would go with the stock OEM or equivalant for they price on them are 50-80 each.

As far as them, the two in the rear is what is reading and sending the information to the computer that htey are working correctly.

 

[sejinv]

Unfortunately all of the places around here charge a minimum of $90-120 dollars just to run the code as part of there diagnostic package, so I would prefer to put that money into replacing both O2 sensors. Also the car has about 75000miles on it and I am certain they have never been replaced so if one has failed, the other one is likely to fail shortly after, if not already, since I had the code checked about a year ago.


Sejin

 

[Lsredy2kstang]

Unfortunately all of the places around here charge a minimum of $90-120 dollars just to run the code as part of there diagnostic package, so I would prefer to put that money into replacing both O2 sensors. Also the car has about 75000miles on it and I am certain they have never been replaced so if one has failed, the other one is likely to fail shortly after, if not already, since I had the code checked about a year ago.


Sejin

Where are you at? Go to the Autozone locally to you if ou are in teh states and they do it for free. You don't have to go to the FORD dealer.

You can get the Sensor wrench and change the rear ones yourself in the driveway. just be careful and let it cool down before doing it.

 

[cruisinV6]

Don't mean to highjack the thread, but when i put my O/R x-pipe on, do I have to get MIL elminators to help correct any computer changes the car will make to the A/F mixture, or is simply just for the SES light?

 

[Lsredy2kstang]

It will throw a SES or CEL. I would suggest getting teh MILS so that it is not on. If you have emmissions that require OBDII readiness and CEL you will have to have them to pass.

 

[98CobraClone]

I went and bought a code reader for $100........but I would do like the others and just change the one that is bad due to the price issues. It's completely up to you, if you want to just change them all at once

 

[cruisinV6]

Thanks Lsred, my SES light has alraedy been on for 2 years, its the secondary air injector that went bad, but it's a pricey thing to get fixed and its only emissions control and we dont have to pass any tests here in MN. So is that the only thing it will do is triger the light?

 

[Lsredy2kstang]

Yeah that is really all it is doing. you can change it yourself and it only costs the part. Check out autozone for a o2 sensor.