52K time for new O2 sensors?

1wildGT · Jan 31, 2007

Changing the X-pipe this weekend, 98 Cobra has 52K on the clock and wondering if I should change the O2 sensor while I'm at it? Do I just change the front two O2 sensors nearest motor or all 4? Aren't the rear O2's just idiot lights for the MIL. The X pipe is a Magnaflow catted, so I souldn't get a MIL (hopefully).

Also, does anyone know if all four sensors are the same or are they location specific.

Superhereaux · Jan 31, 2007

1wildGT said:
Aren't the rear O2's just idiot lights for the MIL.

Also, does anyone know if all four sensors are the same or are they location specific.

the rear o2's do the same thing as the fronts, they read the amount of o2 in the exhaust after the cat and compare it to the fronts to see if the cat is working properly so no, they aren't just idiot lights

as far as a specific location for each i would think the fronts and rears would be different because of the harness lengths. i've yet to do o2's on my car so don't pay any attention to this paragraph

mrvax · Feb 1, 2007

If they ain't broke, don't replace 'em. You would just be wasting money. The rear O2's do not do any adjustments, they just read (and maybe throw a code.)

sgarlic · Feb 1, 2007

I would definately change mine if I had an excuse to.. they aren't like $500 a piece or anything.. just get with Randy and he'll hook you up with some OEM sensors.. I'd change just the fronts.

As said above, the rears are just catalyst monitors (determining whether the catalyst is doing its job,) so unless you're throwing some sort of code, or your MIL is on, I wouldn't bother with them.

LaserRed01GT · Feb 1, 2007

I'd replace the front 2. The if it ain't broke don't fix it theory doesn't apply to 02 sensors. At your mileage, there is a good chance that the 02 sensors are slowing down. You would be able to monitor this with a scanner looking at the crosscounts. Even thought there may not be any HO2S related codes, they may be switching slowly and not allowing the PCM to accurately control the fuel trims.

They're relatively cheap and it's good insurance.

squares98 · Feb 1, 2007

I still have my stockers. 8 years, I guess I need to replace my fronts?

Dragstr05 · Feb 1, 2007

I wouldnt bother. If there was a problem with the O2's, it would set a code. There are numerous O2 codes, including one for "slow response".

DTNODYA · Feb 1, 2007

Dragstr05 said:
I wouldnt bother. If there was a problem with the O2's, it would set a code. There are numerous O2 codes, including one for "slow response".

Yeah, I keep throwing a damn P1151 "Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2." code and I've checked everything for leaks, bad maf, etc, ... must be the O2 I guess.

How much are they?? Both fronts are the same parts right?

1wildGT · Feb 1, 2007

DTNODYA said:
Yeah, I keep throwing a damn P1151 "Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2." code and I've checked everything for leaks, bad maf, etc, ... must be the O2 I guess.

How much are they?? Both fronts are the same parts right?

I think they are $35 to $40 each.

1wildGT · Feb 1, 2007

LaserRed01GT said:
I'd replace the front 2. The if it ain't broke don't fix it theory doesn't apply to 02 sensors. At your mileage, there is a good chance that the 02 sensors are slowing down. You would be able to monitor this with a scanner looking at the crosscounts. Even thought there may not be any HO2S related codes, they may be switching slowly and not allowing the PCM to accurately control the fuel trims.

They're relatively cheap and it's good insurance.

I agree, good insurance. Guess I'll change them while the new X-pipe is sitting here easy to access.

LaserRed01GT · Feb 1, 2007

Dragstr05 said:
I wouldnt bother. If there was a problem with the O2's, it would set a code. There are numerous O2 codes, including one for "slow response".

I was a service manager/writer for several different dealerships in TX. You would be surprised how many people bring in their Ford vehicles complaining of a misfire or fuel mileage problem and come to find out their are no codes set or stored. Then after some testing and inspection we would find all sorts of various things like bad 02's, bad parts in the EVAP, bad sensors, dead misses that were not setting any misfire codes, etc.

DTC's codes are a great tool, but they by no means tell the whole picture.

Dragstr05 · Feb 1, 2007

LaserRed01GT said:
I was a service manager/writer for several different dealerships in TX. You would be surprised how many people bring in their Ford vehicles complaining of a misfire or fuel mileage problem and come to find out their are no codes set or stored. Then after some testing and inspection we would find all sorts of various things like bad 02's, bad parts in the EVAP, bad sensors, dead misses that were not setting any misfire codes, etc.

DTC's codes are a great tool, but they by no means tell the whole picture.

And I agree, as I have seen it. I've seen cars do things that everyone in the shop said it was impossible, tech line said it was impossible, but sure as **** the car was doing it.

My reply was mostly directed to the original post. Only 52k miles, he noted NO driveability problems, and no CEL/codes. Under those conditions, why would you spend money to replace something that isnt causing a problem? If it was running like crap, and no codes and narrowed it down to a few things, sure the O2s are a possiblity but they arent causing a problem here.

Superhereaux · Feb 1, 2007

he just wants to know if he should change them now that they're easily accessable, not whether he should change them just because

kinda like "i've got 78,000 miles on my car and i need a new trans. should i change the clutch while it's out?"

1wildGT · Feb 3, 2007

We'll I bought 4 new Bosch 02 sensors, all of the stock ones look pretty fouled from carbon. The OEM 02 sensors are made by NTK and look pretty cheap compared to the new Bosch ones. Hopefully I won't have to mess with these for at least 100K.

Looks like I answered my own question. 52K had taken its toll on these. Did they still work yeah, but probably not at peak efficiency. Don't wanna chance my new cats on the x-pipe to crappy old sensors that were probably living on borrowed time anyways.

They are a lot cheaper at oxygensensors.com ($41) compared to the various autoparts stores ($59 NAPA to $65 O'reilly). You can also get the splice in type for a few bucks cheaper, but I opted to get the OE plug-n-play style.

LaserRed01GT · Feb 3, 2007

1wildGT said:
We'll I bought 4 new Bosch 02 sensors, all of the stock ones look pretty fouled from carbon. The OEM 02 sensors are made by NTK and look pretty cheap compared to the new Bosch ones. Hopefully I won't have to mess with these for at least 100K.

Looks like I answered my own question. 52K had taken its toll on these. Did they still work yeah, but probably not at peak efficiency. Don't wanna chance my new cats on the x-pipe to crappy old sensors that were probably living on borrowed time anyways.

They are a lot cheaper at oxygensensors.com ($41) compared to the various autoparts stores ($59 NAPA to $65 O'reilly). You can also get the splice in type for a few bucks cheaper, but I opted to get the OE plug-n-play style.

The Bosch 02 sensors are a quality sensor. Preventative maintenance is key, and you are on the right track and wise for doing this.

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