will the O2 sensors throw a code when they need to be replaced?

[sehaare]

I never thought that I'd be keeping the XLT this long so I've never changed an O2 sensor on it. Do they have to replaced after a certain miles (like I seen on other cars) or do you wait until you get a code for a bad O2 sensor?

Thanks
Steve

 

[koda2000]

Not necessarily. Check your tail pipe. Is it black and sooty? Do you have more than 120,000 miles on your originals?

 

[sehaare]

XLT isn't here right now, but I don't remember black and sooty does have just under 150K mile on it though. I've changed O2 sensors on other cars and it has never been a fun time.

 

[sehaare]

I just checked the prices and it looks like there are three O2 sensors for about $25 each which isn't too bad. How hard is it to get to them?

Bosch is recommending changing out at 100K miles

Thanks

 

[fast_dave]

sehaare,

O2 Sensors have a life, and slowly degrade, eventually throwing a Check Engine Light.

On a 98 with 4.0 OHV they (3) are easily accessible.

I don't know what engine you have in your EX.

Regardless, BOSCH is the OEM supplier so the BOSCH replacements are "Plug & Play."

Right before you start the swap out process, disconnect your battery.

The short answer to why you do this is when you're done, and you re-connect the battery, the PCM (computer) will sense and "learn" that you have replaced your 02 sensors. This will initiate a computer program to re-trim the air-fuel mixture parameters as you drive. It's take a few days for the computer to re-learn the parameters, and you might sense this as you're driving, BUT in the end you'll pick up some MPG and Power.

If you don't disconnect the battery and thus clear the old computer settings, it'll continue to run on the old settings = sucking gas and poor performance.

NOTE: Spend and extra 5 minutes and clean the MAF sensor with MAF Sensor cleaner at the same time you replace your 02 sensors. This will assist in gaining more MPG and Power. The MAF, O2 Sensors, and PCM (Computer) all work together to constantly control air/fuel trim. There's also some other components but these are the 3 main ones that have the most effect.

Despite NOT getting a check engine light, I've replaced my O2 sensors (3) times = every 60,000 miles. My EX runs like a bat out of hell each time they're changed, compared to the old ones. The MPG increase and Power gained far outweigh the cost of purchase from Rock Auto (with the 5% Forum Discount), and the 1 hour labor. Every two years when I have to get smog tested in the PRK, the smog tech always comments on how clean and smooth it's running.

YMMV - and opinions vary widely on the subject

PS - Get the 02 sensor socket for $5 - or don't - YMMV

 

[lobo411]

One thing that makes them hard to change is not changing them at the proper interval. The longer they stay in, the more they get welded to the exhaust line.

 

[imp]

O2 Sensors early in the game were different. Today's, like back to the maybe mid-'90s on, they have a heater in them. Occasionally, a CEL is thrown which is caused by one of the O2 Sensors' heaters having burned out. OR, the fuse feeding the heaters has blown.

Therefore, if a code is thrown, check the fuse first. imp

 

[sehaare]

One thing that makes them hard to change is not changing them at the proper interval. The longer they stay in, the more they get welded to the exhaust line.

I had one that was way in the back under the hood on old VW that was the original sensor and I soaked for days in kroil. When I finally put a wrench on it I had to lock my knees in the wheel wells because I had to use so much force to break it free that it was pulling my 200Lbs up off the ground.

 

[lobo411]

I had one that was way in the back under the hood on old VW that was the original sensor and I soaked for days in kroil. When I finally put a wrench on it I had to lock my knees in the wheel wells because I had to use so much force to break it free that it was pulling my 200Lbs up off the ground.

Same here...except I tore out the threads on mine and had to take the Y pipe to an exhaust shop to have a new bung welded in!

 

[fast_dave]

Included within each replacement BOSCH O2 sensor box, is a tube of copper based anti-seize to spread on the bung threads of the new sensors

 

[alohamonte]

I'm at 225k with the original O2s... I have a set in the tool box but haven't gotten around to checking them. This thread is making me think I should prioritize that.

 

[sehaare]

I'm at 225k with the original O2s... I have a set in the tool box but haven't gotten around to checking them. This thread is making me think I should prioritize that.

Yep I've moved them up on my list to right after I flush the coolant (now in progress on a saturday morning).

I 've got the sensors coming from rockauto and broke down and got a snap on O2 sensor socket coming, started spraying down the old ones with Kroil this morning so hopefully that will help some by the time the new ones show up.

Planning on pulling the front seats and center console to get to the access cover for the rear one, and while they are out fix the driver seats rocking and adding heated seat pads to it.

 

[lobo411]

Yep I've moved them up on my list to right after I flush the coolant (now in progress on a saturday morning).

I 've got the sensors coming from rockauto and broke down and got a snap on O2 sensor socket coming, started spraying down the old ones with Kroil this morning so hopefully that will help some by the time the new ones show up.

Planning on pulling the front seats and center console to get to the access cover for the rear one, and while they are out fix the driver seats rocking and adding heated seat pads to it.

YMMV, but I found the post-cat o2 sensor on my OHV to be the easiest one to get out. I changed it in 10 mins using an ordinary box wrench. I figured it must be a lot cooler back there, so it's less likely to be welded in. But YMMV.

The two on the Y-pipe were the hardest to do. I got the driver's side one done with some difficulty, but I ended up having to drop the Y-pipe to do the passenger's side one. Had I known that, I would have just dropped the Y pipe in the first place and saved myself a ton of pain.

Having said that, mine is a California car and the exhaust system/underbody is basically like brand new.

 

[lobo411]

Included within each replacement BOSCH O2 sensor box, is a tube of copper based anti-seize to spread on the bung threads of the new sensors

My new ones came with a dab already on the threads. I kinda wonder what they do at the factory. Is it that they don't do the anti-seize, is it that it doesn't last 150000 mi, or is it that the pre-cat pipe is too hot for the a/s to really work?